To improve a convenience upon adjusting a voice output during communication.

A camera 4C is attached to a cabinet of a mobile electronic device, and a portion acquiring images is exposed to the outside of the cabinet. A receiver 6 is controlled by a voice processor 14 and outputs a voice. When a volume of the receiver 6 is adjusted, the camera 4C is covered by fingers of a user of a mobile electronic device 1. A main processor 11 of a control device 10 adjusts the volume of the voice outputted from the receiver 6 based on an image of the fingers of the user covering an input light portion of the camera 4C, the image being taken by the camera 4C.