Fuel cell apparatus of a compact size using a hydrogen storage alloy, in which heat can be efficiently transmitted from fuel cell bodies to the hydrogen storage alloy. The fuel cell apparatus includes a plurality of fuel cell bodies (1), a hydrogen storage tank (3), a hydrogen supply device for supplying hydrogen to the fuel cell bodies from the hydrogen storage tank, an air feed device (2) for supplying the air, supplying oxygen, a secondary battery (8), and a casing receiving the above components therein, and the casing (10) has air intake ports (11) and an air discharge port (12) for the air feed device, and is formed into such a construction as to enable the hydrogen storage tank to be introduced into and removed from the casing. The hydrogen storage tank for supplying anode fuel to the fuel cell bodies is disposed on that side surface of each of at least one pair of fuel cell bodies, facing away from a cathode fuel-supplying inlet thereof, through a heat transmission device (9). With this construction, the energy of heat, generated by the fuel cell bodies, is efficiently transmitted to the hydrogen storage tank, and the stable supply of the hydrogen can be achieved, and the whole of the power system can be formed into a compact design.