An imaging system has a lens unit including an imaging device which converts an optical image representing an object into image data by an imaging unit, a main body unit which holds the lens unit in such a manner that the lens unit is attachable to and detachable from the main body unit and a controller configured, by use of an integrated firmware in which one or a plurality of firmwares of the lens unit and one or a plurality of firmwares of the main body unit are integrated, to exchange the integrated firmware between the lens unit and the main body unit via a communication device, and to upgrade one of the firmwares with a corresponding firmware in the integrated firmware.