To provide a photovoltaic power generating system that makes it possible to be connected to a commercial system in an easy way and that is capable of supplying generated electric power to loads connected to the commercial system, even if the system has a battery.

This system comprises a solar cell module 1 and a power-converting section. The power-converting section is mounted on the solar cell module in a detachably mountable state. As the power-converting portion, an independent power supply unit 10a, including the battery or a connecting unit provided with a system protecting function with respect to commercial system, is used. The system is provided with a structure that prevents the simultaneous connection of both units to a module output terminal 2.