A portable terminal device has enclosures with a movable portion, a display section that displays visible information showing an operation target area, and a touch sensor that detects a position on a display screen of the display section touched by a user's finger, or the like. A shape detection section detects a change in the shape of the enclosure; an input operation management section manages a position detected by the touch sensor and an operation target area of each of pieces of visible information displayed on the display section in an associated manner; and a display control section automatically makes a change to at least display positions of the respective pieces of visible information about the operation target displayed on the display section in accordance with a change in shape of the enclosure detected by the shape detection section.