In a fuel cell system, a compressor used for supply of a gas and a motor are arranged to be opposed to each other across a transmission mechanism, such that a motor driveshaft is placed to face rotating shafts of the compressor. Such opposed arrangement enables the motor and the compressor to be relatively close to each other across only a narrow distance required for the transmission mechanism. Additionally, a circulation pump used for supply of a coolant is placed, such that the motor driving force is transmitted from the motor driveshaft to the circulation pump directly or via the transmission mechanism.