Provided is a technology of allowing operation of four push buttons of a controller including the four push buttons provided in place of a cross key pad as if operating the cross key pad. The controller includes a third push-button input module (142) being a cylindrical recess including four push buttons (142A to 142D) on a bottom surface of the third push-button input module (142). A recessed portion (142E) is formed in the bottom surface. Meanwhile, the controller includes a cover member (200) having a circular plate portion (211) including a cross-key-pad portion (212). A column portion having a circular column shape is provided on a back surface of the cover member (200). The cover member (200) is fixed to the third push-button input module (142) through insertion of the column portion into the recessed portion (142E). When a user presses the cross-key-pad portion (212), freely selected one of the four push buttons (142A to 142D) positioned below the circular plate portion (211) can be pressed.