PROBLEM TO BE SOLVED: To provide a method for producing an alkali metal sulfide that can greatly reduce the consumption of sulfide gas.SOLUTION: The method for producing an alkali metal sulfide gas includes: introducing sulfide into a reaction tank storing an alkali metal hydroxide and a solvent; bringing the alkali metal hydroxide into contact with the sulfide gas to produce an alkali metal sulfide; taking out the sulfide gas that has not been consumed by the contact from the reaction tank; and introducing the taken-out sulfide gas into the reaction tank.
