On each of upper and lower surfaces of a flat-plate-like support substrate having a longitudinal direction and having fuel gas flow channels formed therein, a plurality of power-generating elements A connected electrically in series are disposed at predetermined intervals along the longitudinal direction. On each of the upper and lower surfaces of the support substrate, a plurality of recesses are formed at predetermined intervals along the longitudinal direction. Each of the recesses is a rectangular-parallelepiped-like depression defined by four side walls arranged in a circumferentially closed manner and a bottom wall. That is, in the support substrate, frames are formed to surround the respective recesses. Fuel electrodes of the power-generating elements A are embedded in the respective recesses.