A touch panel device is provided which, even in cases in which a plurality of GUI parts are arranged in a limited space, enables operation of a GUI part in which, unlike a physical button, it is hard to distinguish the boundary by touch, without operational error, using a finger with a very large contact area in comparison to a touch pen. A touch panel device includes a rectangular screen having a detection region which detects contact, and a control section for generating a control signal in response to the contact detected by the detection region. The detection region has a shape that is inclined with respect to a side edge of the rectangular screen. In cases in which a body-part used for the contact is a finger of a user; when the user uses the right hand, the detection region has a shape that is inclined to the left side with respect to the side edge of the rectangular screen; and when the user uses the left hand, the detection region has a shape that is inclined to the right side with respect to the side edge of the rectangular screen.