There is provided an intercom system capable of reducing power consumption by stably performing wireless communication between a camera and a monitor. Monitor 200 checks whether or not a communication error occurs in image data received from camera 100, and checks whether or not there is a slot as a moving destination in an empty state in a case where the communication error occurs. In a case where there is no slot as the moving destination, monitor 200 controls the number of connected image calls by transmitting an image call disconnect request to camera 100. Accordingly, intercom system 10 varies image quality (a frame rate, a compression ratio, or an image size) depending on a radio wave status.