To provide a method of manufacturing an impeller, which can smooth a polished surface without undulation in removing an alteration layer generated on an electrical-discharge-machining surface by wet polishing after a channel is formed by electrical discharge machining.

A method of manufacturing an impeller includes a channel formation step of forming a channel 14 from an inlet 141 to an outlet 142 of a gas by electrical discharge machining, and a wet polishing step of wet-polishing an inner wall of the channel 14 by soaking the impeller 10 in a polishing liquid. In the wet polishing step, a first nozzle 20 and a second nozzle 30 which suck the polishing liquid toward the outside of the channel 14 are inserted into the channel 14.