When a ground fault occurs in some solar battery string, this solar battery string may be disconnected and operation of a solar power generation system may be continued. If the open-circuit voltage of the solar battery string is high, a safety problem arises. If the open-circuit voltage is decreased, the conversion efficiency decreases. Therefore, an intermediate switch is provided midway along the solar battery string. When a ground fault occurs, this solar battery string where the ground fault has occurred is divided into substrings.