To provide a significantly cost-reduced solar light utilizing device which plays a great role in the future, by accumulating effects of hot water supply, heating preventing function of a roof where the device installed, as well as solar power generation function, and integrating improvement in power generation efficiency.

A solar light utilizing device includes a flow path through which a plurality of fluids pass, as a base plate of a solar light power generation panel. A first fluid passage of the base plate forms a water stream system equipped with a water supply part, a connection pipe, and a flow rate adjusting valve. A second gas passage is equipped with a ventilation device containing an opening/closing plate for controlling gas flow rate.