PURPOSE: To improve electricity generating efficiency against the loaded raw fuel material by reforming non-reactive components of the raw fuel material supplied to the electrochemical reaction part without being reformed in a reforming part and re-circulating them to the electrochemical reaction part.

CONSTITUTION: A first reforming part 4 in which a raw fuel gas is supplied and reformed into a fuel gas of mainly hydrogen gas is installed in a supplying inlet side of a fuel gas flowing route 2 and a second reforming part 20 in which hydrocarbons, such as methane, etc., in a waste fuel gas discharged out of the fuel gas flowing route 2 are reformed into hydrogen by a reforming catalyst 6 is installed in a discharging outlet side of the fuel gas flowing route 2. Consequently, not reacted components contained in the waste fuel gas discharged out of the electrochemical reaction part 1 are reformed efficiently in the reforming parts 4, 20 and the reformed gas is circulated again to the electrochemical reaction part 1. As a result, electricity generating efficiency of a battery is improved.