An air conditioner includes a body including an air inlet configured to receive air from an air compressor configured to press and transfer the air to provide the air to a cathode of a fuel cell stack. An air element is configured to supply the air to the cathode, and an inner space allows the air inlet and the air outlet to communicate with each other. A plurality of tubes is provided in the inner space of the body and through which fluid flows along hollows holes of the tubes. While the air supplied through the air inlet passes through the inner space, the air is cooled through heat exchange with the fluid flowing along the hollows of the tubes.