A game system as an information processing system includes a game apparatus and a controller, and the controller is attached with an attachment device. The controller images an image including infrared rays output from markers arranged on a monitor through a half mirror integrated in the attachment device. Furthermore, the controller images an image including an infrared ray from a pen input device reflected by the half mirror via a touch panel. In the former, the controller functions as an input device for a direct coordinate input, and in the latter, the controller functions as a pen tablet.