Abstract: A fuel battery in which a gas communication passage, wide in relation to the thickness of the unit cell, is provided and sufficient gas can be supplied to a generating section even if the fuel battery is made thin. A spacer and a separator are stacked. The spacer has a vent step groove where gas passes and a fitting step groove closed by the separator. The step grooves are formed between a square opening disposed in the center and containing a generating section and vent holes constituting manifolds. The separator has a projecting section projecting toward the fitting step groove and disposed between a gas supply section opposed to the generating section and the vent holes constituting the manifolds. The separator further has a communication groove for communicating with the projecting section along the vent holes and the gas supply section. The vent step groove is connected to the communication groove.