<p>To alleviate or avoid uncomfortable feeling and motion sickness of a user likely to be caused by watching a display screen when a portable terminal device is used during traveling on a vehicle. A movement detecting means (104) such as an acceleration sensor detects the vibration or movement of the portable terminal device, a moving distance calculating means (105) calculates the moving distance of a display screen according to the detected movement information, and an image converting means (102) shifts the display position of image information to be displayed in a direction opposite to the moving direction of the display screen. The above arrangement prevents the user's line of sight watching the screen of the portable terminal device from irregularly moving in response to the vibration of a vehicle.</p>
