In case where a key having a detection region (inner frame) in which user's instructions can be accepted is displayed according to a certain operation status of an apparatus, and in case where there is an invalid region in which the user's instruction is not detectable is adjacent to a key display region (outer frame) of the key, the detection region of the key is caused to be larger than the key display region by utilizing the invalid region. Moreover, the detection region is expanded/shrunk according to key arrangement and a number of keys to be displayed. With this, the detection region of the key is expanded/shrunk according to according to the key arrangement on the screen in a display-cum-operation device in which a display device and a coordinate input device are integrated.