The present invention provides a camera system including: an imaging unit which has an image-taking optical system and an image pickup device; and a main unit which receives image signals from the imaging unit and performs signal processing. The imaging unit includes an identification section for identifying the main unit. When the imaging unit is attached to the main unit and the power is supplied from the main unit to the imaging unit, the imaging unit issues to the main unit a request for the transmission of the identification code. In response to the request, the main unit sends the identification code to the imaging unit. The identification section of the imaging unit identifies the main unit based on the received identification code.