Provided is a game system utilizing the LEDs of a controller (20). In a game system (1), an image pickup device (2) takes the image of the controller (20). The controller (20) includes a plurality of input units for performing an operation input to proceed a game, and a plurality of LEDs for expressing a controller number to be set in the controller (20), in a game application to be executed. A game device (10) accepts and reflects the operation input of the controller (20), upon the processing of the game application, acquires the taken image from the image pickup device (2), acquires a position in the taken image of the controller (20) from the positions of the LEDs in the taken image, reflects the acquired position information upon the processing of the game application, and generates an image signal indicating the application processing result based on the operation input and the acquired position information.