PROBLEM TO BE SOLVED: To provide a cooling device of a solar cell panel which achieves high cooling performance utilizing evaporative latent heat of a coolant and excellent maintainability.SOLUTION: A cooling device A of a solar cell panel 3 includes: a coolant tank 6 disposed below the solar cell panel 3; and a water retention member 11 disposed in the coolant tank 6, causing a coolant a supplied to the coolant tank 6 to penetrate thereinto, and thereby retaining the coolant a. A space 12 is formed between a lower surface of the solar cell panel 3 and an upper surface of the water retention member 11. In the structure, the temperature of air in the space 12 is decreased to a low temperature due to evaporative latent heat of the coolant a evaporated on the surface of the water retention member 11 and the solar cell panel 3 is cooled. The water retention member 11 may be replaced independently from the solar cell panel 3 and achieves excellent maintainability.