A mobile terminal device provided with a plurality of keys includes: a touch pad and a touch detection interface which detect a user touching a key; a press detection interface which detects the user pressing the key; a display unit which sequentially displays characters, as candidate characters, assigned to the key pressed by the user, when the press detection interface detects the user pressing the key; and a controller which converts the candidate character displayed on the display unit to a finalized character, when an untouched time period during the user does not touch the pressed key reaches a predetermined judging time after the press detection interface detects the user pressing the key.