A peripheral device adapted for connecting to a mobile device is provided. The peripheral device includes a main body, at least one connecting arm, and at least one control module. The main body includes a clamping unit to clamp a mobile device in place. One end of the connecting arm is movably connected to one side of the main body, the connecting arm is movable and close to the one side of the main body to be in a storage position, or extends away from thereof to be in an expanded position. Each of the control modules includes at least one input unit, and the control module is detachably connected to another end of the connecting arm. When the connecting arm is in the expanded position, the control module is electrically connected to the mobile device, so as to provide control thereof.