A cuprous oxide fine particle production method includes a production step of producing cuprous oxide fine particles using copper compound powder and a thermal plasma flame. The thermal plasma flame is derived from an inert gas. The production step includes a step of supplying into the thermal plasma flame, the copper compound powder dispersed using a carrier gas or slurry obtained by dispersing the copper compound powder in water in the form of droplets. The production step preferably further includes a step of supplying a cooling gas to an end portion of the thermal plasma flame.