A development assistance device that assists a user in examining display settings of each of a plurality of character strings (CS 1, CS2, CS3), each of which is displayed in a corresponding one of a plurality of display modes, the development assistance device comprising: an image display unit that displays an image having a size corresponding to the size of a display region commonly allocated to the plurality of character strings (CS1, CS2, CS3); and a character display unit that simultaneously displays the plurality of character strings (CS1, CS2, CS3) over the image displayed by the image display unit; the development assistance device characterized in that: the character display unit superimposes and displays all of the plurality of character strings (CS1, CS2, CS3) in a semi-transparent color, the size of the display region is the size of a display region of a graphical user interface component, the development assistance device further comprising: an image operation reception unit that receives a user operation for changing the size of the image displayed by the image display unit, wherein when the user operation is received by the image operation reception unit, the image display unit displays the image whose size has been changed in accordance with the user operation; and a character operation reception unit that receives a user operation for changing at least one of the character font and the character size of at least one character string (CS 1, CS2, CS3) of the plurality of character strings (CS 1, CS2, CS3) displayed by the character display unit, wherein when the user operation is received by the character operation reception unit, the character display unit changes at least one of the character font and the character size of the character string (CS1, CS2, CS3) being a target of the user operation in accordance with the user operation, and displays the changed character string (CS1, CS2, CS3), an image display unit that displays an image having a size corresponding to the size of a display region commonly allocated to the plurality of character strings (CS1, CS2, CS3); and a character display unit that simultaneously displays the plurality of character strings (CS1, CS2, CS3) over the image displayed by the image display unit; the development assistance device characterized in that: the character display unit superimposes and displays all of the plurality of character strings (CS1, CS2, CS3) in a semi-transparent color, the size of the display region is the size of a display region of a graphical user interface component, the development assistance device further comprising: an image operation reception unit that receives a user operation for changing the size of the image displayed by the image display unit, wherein when the user operation is received by the image operation reception unit, the image display unit displays the image whose size has been changed in accordance with the user operation; and a character operation reception unit that receives a user operation for changing at least one of the character font and the character size of at least one character string (CS 1, CS2, CS3) of the plurality of character strings (CS 1, CS2, CS3) displayed by the character display unit, wherein when the user operation is received by the character operation reception unit, the character display unit changes at least one of the character font and the character size of the character string (CS1, CS2, CS3) being a target of the user operation in accordance with the user operation, and displays the changed character string (CS1, CS2, CS3), an image operation reception unit that receives a user operation for changing the size of the image displayed by the image display unit, wherein when the user operation is received by the image operation reception unit, the image display unit displays the image whose size has been changed in accordance with the user operation; and a character operation reception unit that receives a user operation for changing at least one of the character font and the character size of at least one character string (CS 1, CS2, CS3) of the plurality of character strings (CS 1, CS2, CS3) displayed by the character display unit, wherein when the user operation is received by the character operation reception unit, the character display unit changes at least one of the character font and the character size of the character string (CS1, CS2, CS3) being a target of the user operation in accordance with the user operation, and displays the changed character string (CS1, CS2, CS3),