diff --git a/ast/ast.go b/ast/ast.go
index a5c2686e..85fdcb7d 100644
--- a/ast/ast.go
+++ b/ast/ast.go
@@ -227,21 +227,14 @@ func (bs *BlockStatement) String() string {
 }
 
 // Represent function statement
-type FunctionStatement struct {
-	Name       *Identifier
-	Parameters []*ParameterLiteral
+type ExpressionStatement struct {
+	Expr Expression
 }
 
-func (fs *FunctionStatement) do() {}
+func (es *ExpressionStatement) do() {}
 
-func (fs *FunctionStatement) String() string {
-	var out bytes.Buffer
-	out.WriteString(fs.Name.String() + "(")
-	for _, parameter := range fs.Parameters {
-		out.WriteString(parameter.String())
-	}
-	out.WriteString(")")
-	return out.String()
+func (es *ExpressionStatement) String() string {
+	return es.Expr.String()
 }
 
 // Represent string literal
diff --git a/parse/parser.go b/parse/parser.go
index 3cb749ee..98c3d023 100644
--- a/parse/parser.go
+++ b/parse/parser.go
@@ -260,10 +260,7 @@ func parseStatement(buf TokenBuffer) (ast.Statement, error) {
 	case Return:
 		return parseReturnStatement(buf)
 	default:
-		return nil, parseError{
-			tokenType: tt,
-			reason:    "invalid token for parsing statement",
-		}
+		return parseExpressionStatement(buf)
 	}
 }
 
@@ -648,7 +645,10 @@ func parseCallExpression(buf TokenBuffer, fn ast.Expression) (ast.Expression, er
 // parseCallArguments parse arguments of function call
 func parseCallArguments(buf TokenBuffer) ([]ast.Expression, error) {
 	args := []ast.Expression{}
-	buf.Read()
+	if err := expectNext(buf, Lparen); err != nil {
+		return nil, err
+	}
+
 	if curTokenIs(buf, Rparen) {
 		return args, nil
 	}
@@ -765,3 +765,23 @@ func parseBlockStatement(buf TokenBuffer) (*ast.BlockStatement, error) {
 	}
 	return block, nil
 }
+
+func parseExpressionStatement(buf TokenBuffer) (*ast.ExpressionStatement, error) {
+	stmt := &ast.ExpressionStatement{}
+	tok := buf.Read()
+	if tok.Type != Ident {
+		return nil, parseError{
+			tok.Type,
+			"token is not identifier",
+		}
+	}
+	ident := &ast.Identifier{Value: tok.Val}
+
+	exp, err := parseCallExpression(buf, ident)
+	if err != nil {
+		return nil, err
+	}
+
+	stmt.Expr = exp
+	return stmt, nil
+}
diff --git a/parse/parser_internal_test.go b/parse/parser_internal_test.go
index f3594d0c..df8337cf 100644
--- a/parse/parser_internal_test.go
+++ b/parse/parser_internal_test.go
@@ -1851,7 +1851,7 @@ func TestParseStatement(t *testing.T) {
 				{Type: Rbrace, Val: "}"},
 				{Type: Eol, Val: "\n"},
 			},
-			expectedErr:  parseError{Int, "invalid token for parsing statement"},
+			expectedErr:  parseError{Int, "token is not identifier"},
 			expectedStmt: ``,
 		},
 		{
@@ -1971,7 +1971,7 @@ func TestParseStatement(t *testing.T) {
 			tokens: []Token{
 				{Type: Int, Val: "1"},
 			},
-			expectedErr:  parseError{Int, "invalid token for parsing statement"},
+			expectedErr:  parseError{Int, "token is not identifier"},
 			expectedStmt: ``,
 		},
 	}
@@ -1992,3 +1992,96 @@ func TestParseStatement(t *testing.T) {
 		}
 	}
 }
+
+func TestParseExpressionStatement(t *testing.T) {
+	initParseFnMap()
+
+	tests := []struct {
+		tokens       []Token
+		expectedStmt string
+		expectedErr  string
+	}{
+		{
+			// add()
+			[]Token{
+				{Type: Ident, Val: "add"},
+				{Type: Lparen, Val: "("},
+				{Type: Rparen, Val: ")"},
+			},
+			"function add(  )",
+			"",
+		},
+		{
+			// read(x int)
+			[]Token{
+				{Type: Ident, Val: "read"},
+				{Type: Lparen, Val: "("},
+				{Type: Ident, Val: "x"},
+				{Type: Rparen, Val: ")"},
+			},
+			"function read( x )",
+			"",
+		},
+		{
+			// testFunction(a int, b string)
+			[]Token{
+				{Type: Ident, Val: "testFunction"},
+				{Type: Lparen, Val: "("},
+				{Type: Ident, Val: "a"},
+				{Type: Comma, Val: ","},
+				{Type: Ident, Val: "b"},
+				{Type: Rparen, Val: ")"},
+			},
+			"function testFunction( a, b )",
+			"",
+		},
+		{
+			// testFunction(a int b string) <= error case
+			[]Token{
+				{Type: Ident, Val: "testFunction"},
+				{Type: Lparen, Val: "("},
+				{Type: Ident, Val: "a"},
+				{Type: IntType, Val: "int"},
+				{Type: Ident, Val: "b"},
+				{Type: IntType, Val: "string"},
+				{Type: Rparen, Val: ")"},
+			},
+			"",
+			"INT_TYPE, expectNext() : expected [RPAREN], but got [INT_TYPE]",
+		},
+		{
+			// 1() <= error case
+			[]Token{
+				{Type: Int, Val: "1"},
+				{Type: Lparen, Val: "("},
+				{Type: Rparen, Val: ")"},
+			},
+			"",
+			"INT, token is not identifier",
+		},
+		{
+			// add) <= error case
+			[]Token{
+				{Type: Ident, Val: "add"},
+				{Type: Rparen, Val: ")"},
+			},
+			"",
+			"RPAREN, expectNext() : expected [LPAREN], but got [RPAREN]",
+		},
+	}
+
+	for i, test := range tests {
+		stmt, err := parseExpressionStatement(&mockTokenBuffer{test.tokens, 0})
+		if stmt != nil && stmt.String() != test.expectedStmt {
+			t.Fatalf("test[%d] - TestParseFunctionStatement wrong answer.\n"+
+				"expected= %s\n"+
+				"got= %s", i, test.expectedStmt, stmt.String())
+		}
+
+		if err != nil && err.Error() != test.expectedErr {
+			t.Fatalf("test[%d] - TestParseFunctionStatement wrong error.\n"+
+				"expected= %s\n"+
+				"got= %s", i, test.expectedErr, err.Error())
+		}
+	}
+}