diff --git a/CHANGELOG.md b/CHANGELOG.md
index 20004ac..4df3cb3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,7 @@ All notable changes to this project will be documented in this file. The format
  - remove-shell command.
  - reset command.
  - sync command.
+ - valid-shell command.
 ### Changed
  - Project
    - the classification of directories under internal/applets.
diff --git a/docs/introduction/en/CommandAppletList.md b/docs/introduction/en/CommandAppletList.md
index 886cff9..b652931 100644
--- a/docs/introduction/en/CommandAppletList.md
+++ b/docs/introduction/en/CommandAppletList.md
@@ -55,6 +55,7 @@
 |  unexpand| Convert N space to TAB (default:N=8)|
 |  unix2dos| Change LF to CRLF|
 |   uuidgeb| Print UUID (Universal Unique IDentifier|
+|  valid-shell| Verify if /etc/shells is valid|
 |    wc    |    Word Counter|
 |    wget  | The non-interactive network downloader|
 |    which | Returns the file path which would be executed in the current environment|
diff --git a/internal/applets/applet.go b/internal/applets/applet.go
index 8a68121..c4ec6fd 100644
--- a/internal/applets/applet.go
+++ b/internal/applets/applet.go
@@ -47,6 +47,7 @@ import (
 	"github.com/nao1215/mimixbox/internal/applets/mbutils/path"
 	"github.com/nao1215/mimixbox/internal/applets/mbutils/sddf"
 	"github.com/nao1215/mimixbox/internal/applets/mbutils/serial"
+	validShell "github.com/nao1215/mimixbox/internal/applets/mbutils/valid-shell"
 	"github.com/nao1215/mimixbox/internal/applets/shellutils/base64"
 	"github.com/nao1215/mimixbox/internal/applets/shellutils/basename"
 	"github.com/nao1215/mimixbox/internal/applets/shellutils/chroot"
@@ -148,6 +149,7 @@ func init() {
 		"unexpand":     {unexpand.Run, "Convert N space to TAB(default:N=8)"},
 		"unix2dos":     {unix2dos.Run, "Change LF to CRLF"},
 		"uuidgen":      {uuidgen.Run, "Print UUID (Universal Unique IDentifier"},
+		"valid-shell":  {validShell.Run, "Verify if /etc/shells is valid"},
 		"wc":           {wc.Run, "Word Count"},
 		"wget":         {wget.Run, "The non-interactive network downloader"},
 		"which":        {which.Run, "Returns the file path which would be executed in the current environment"},
diff --git a/internal/applets/mbutils/valid-shell/valid-shell.go b/internal/applets/mbutils/valid-shell/valid-shell.go
new file mode 100644
index 0000000..7cd42aa
--- /dev/null
+++ b/internal/applets/mbutils/valid-shell/valid-shell.go
@@ -0,0 +1,168 @@
+//
+// mimixbox/internal/applets/debianutils/valid-shell/valid-shell.go
+//
+// Copyright 2021 Naohiro CHIKAMATSU
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package validShell
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+
+	"github.com/jessevdk/go-flags"
+	mb "github.com/nao1215/mimixbox/internal/lib"
+)
+
+const cmdName string = "valid-shell"
+
+const version = "1.0.0"
+
+var osExit = os.Exit
+
+type options struct {
+	Show    bool `short:"s" long:"show" description:"Print contents of /etc/shells"`
+	Fix     bool `short:"f" long:"fix" description:"Fix problems in /etc/shells"`
+	Version bool `short:"v" long:"version" description:"Show valid-shell command version"`
+}
+
+// Exit code
+const (
+	ExitSuccess int = iota // 0
+	ExitFailuer
+)
+
+func Run() (int, error) {
+	var opts options
+	var err error
+
+	if _, err = parseArgs(&opts); err != nil {
+		return ExitFailuer, nil
+	}
+
+	return validShell(opts)
+}
+
+func validShell(opts options) (int, error) {
+	if opts.Show {
+		return printShellsFile()
+	} else if opts.Fix {
+		return fix()
+	}
+	return valid()
+}
+
+func printShellsFile() (int, error) {
+	lines, err := mb.ReadFileToStrList(mb.ShellsFilePath)
+	if err != nil {
+		return ExitFailuer, err
+	}
+	for _, v := range lines {
+		fmt.Fprintf(os.Stdout, "%s", v)
+	}
+	return ExitSuccess, nil
+}
+
+func fix() (int, error) {
+	f, err := os.OpenFile(mb.TmpShellsFile(), os.O_CREATE|os.O_WRONLY, 0644)
+	if err != nil {
+		return ExitFailuer, err
+	}
+	defer f.Close()
+
+	lines, err := mb.ReadFileToStrList(mb.ShellsFilePath)
+	if err != nil {
+		return ExitFailuer, err
+	}
+
+	lines = mb.ChopAll(lines)
+	for _, v := range lines {
+		if strings.HasPrefix(v, "#") {
+			fmt.Fprintln(f, v)
+			continue
+		}
+		if isFalseCmd(v) {
+			continue // NG: Bupass
+		}
+		if mb.Exists(v) {
+			fmt.Fprintln(f, v)
+		} // else is NG: Bypass
+	}
+
+	err = mb.Copy(mb.TmpShellsFile(), mb.ShellsFilePath)
+	if err != nil {
+		mb.RemoveFile(mb.TmpShellsFile(), false)
+		return ExitFailuer, err
+	}
+	mb.RemoveFile(mb.TmpShellsFile(), false)
+
+	return ExitSuccess, nil
+}
+
+func valid() (int, error) {
+	lines, err := mb.ReadFileToStrList(mb.ShellsFilePath)
+	if err != nil {
+		return ExitFailuer, err
+	}
+
+	lines = mb.ChopAll(lines)
+	for _, v := range lines {
+		if strings.HasPrefix(v, "#") {
+			continue
+		}
+		if isFalseCmd(v) {
+			fmt.Fprintf(os.Stdout, "NG: %s (not preferable for security)\n", v)
+			continue
+		}
+		if mb.Exists(v) {
+			fmt.Fprintf(os.Stdout, "OK: %s\n", v)
+		} else {
+			fmt.Fprintf(os.Stdout, "NG: %s (not exist in the system)\n", v)
+		}
+	}
+	return ExitSuccess, nil
+}
+
+func isFalseCmd(str string) bool {
+	path, err := exec.LookPath("false")
+	if err != nil {
+		return false
+	}
+	return path == str
+}
+
+func parseArgs(opts *options) ([]string, error) {
+	p := initParser(opts)
+
+	args, err := p.Parse()
+	if err != nil {
+		return nil, err
+	}
+
+	if opts.Version {
+		mb.ShowVersion(cmdName, version)
+		osExit(ExitSuccess)
+	}
+
+	return args, nil
+}
+
+func initParser(opts *options) *flags.Parser {
+	parser := flags.NewParser(opts, flags.Default)
+	parser.Name = cmdName
+	parser.Usage = "[OPTIONS]"
+
+	return parser
+}