PROBLEM TO BE SOLVED: To provide a fine mist cooling method and a fine mist cooling system of a plant cultivation facility which are capable of realizing a cooling function and a carbon dioxide gas application function by a simple configuration and preventing inconvenience such as condensation.SOLUTION: A spray device which is equipped with: a nozzle 7 which ejects two-fluid fine mist M； a gas passage 8 which supplies compressed carbon dioxide gas from a carbon dioxide gas cylinder 3 to the nozzle 7； and a water path 9 which supplies water W to the nozzle 7 is disposed in a plant cultivation facility, and the fine mist M created by mixing the compressed carbon dioxide gas with the water W is ejected from the nozzle 7. Not only cooling operation and carbon dioxide gas application are performed simultaneously in the plant cultivation facility to improve work efficiency, but also the carbon dioxide gas cylinder 3 is used as a power source for creating fine mist M.
