First and second fuel cell stacks having a simple and compact structure are connected in parallel to each other to enable ensuring a desired electric power generating performance. The first and second fuel cell stacks have the same structure and are arranged in parallel to each other with polarities thereof reversed. A manifold piping is mounted to one ends of the first and second fuel cell stacks. In order to supply an oxidizer gas, a fuel gas, and a coolant to the first and second fuel cell stacks, at least an oxidizer-gas supply pipe, a fuel-gas supply pipe, and a coolant supply pipe in the manifold piping are provided to be symmetrical with respect to the first and second fuel cell stacks.