To provide a water quality-cleaning system by utilizing sunlight, performing the growth of algae, diatom, bacteria, etc., by photosynthesis, cleaning the water quality by decomposing sludge containing phosphorus, nitrogen, etc., and culturing fishes by illuminating places where the sunlight does not reach and also exposing with air by using a pump, in lakes, ports, dams, etc.

This water quality-cleaning system by utilizing the sunlight includes an electric power-obtaining device equipped with a solar electricity generation panel 11, and a controller 32 for regulating the electric voltage and wave length of the electric power generated by the solar electricity-generating panel 11, a fluid-transporting device driven by the electric power supplied from the electric power-obtaining device, and an LED illumination device 31 emitting light by the electric power supplied from the electric power-obtaining device.