An image acquisition section 105 obtains an image of a finger by bringing the finger into touch with a display 13 formed of a device including an image pickup device and picture elements or by bringing the finger closer to the display without touching the display. A computing section 120 determines a center-of-gravity position of the finger, based on the obtained image of the finger. An information generating section 125 generates information for operating the cellular phone based on a displacement of the center-of-gravity position of the finger r. A determination section 115 determines whether the finger has touched the screen or not, based on the touch area between the finger and the screen. A display section 130 displays a virtual sign 14 indicating a reference point for subsequent movement of the finger, at a first position that the finger has touched the screen.