The present invention comprises fuel cells 84 disposed within a fuel cell module 2, a reformer 20, a reformer temperature sensor 148 for detecting a reforming state temperature, and a control section 110 for controlling the operation of the fuel cell module. The control section prohibits the normal startup POX and executes a restart control different from the normal startup POX when the reforming state temperature is at least in a high temperature region within the POX temperature band in a state in which the operation of the solid oxide fuel cell module is stopped.