According to one embodiment, a cell stack of a fuel cell device comprises a positive electrode including a anode separator, and a pair of anode plates laminated opposite first and second contact surfaces of the anode separator, a pair of negative electrodes laminated individually on the opposite sides of the positive electrode, and electrolyte layers. The negative electrode includes a cathode plate opposed to each corresponding anode plate with a gap therebetween and a cathode separator provided with a contact surface opposed to the cathode plate. The anode separator includes first fuel channels formed in the first contact surface, second fuel channels formed in the second contact surface, and cooling channels formed between the first and second contact surfaces and through which a coolant is circulated. The cathode separator includes a plurality of air channels formed in the contact surface and through which air is supplied to the cathode plate.