To provide a manufacturing method of an impeller which, after forming a fluid channel by electric discharge processing, is capable of removing an altered layer generated on an electric-discharge processed surface of the fluid channel, without concern about corrosion.

A manufacturing method of an impeller 10 for a centrifugal rotating machine includes: a fluid channel forming step for forming a fluid channel 14 from an inlet 141 for gas to an outlet 142 by applying electric discharge processing; and a polishing step for spraying a particulate abrasive material on inner walls demarcating the fluid channel 14. In the polishing step, there is inserted into the fluid channel, a nozzle in which a plurality of jet holes are formed for jetting the abrasive material toward the inner walls of the fluid channel 14, and by spraying the abrasive material on the inner walls while moving the nozzle back and forth within the fluid channel 14, the inner walls of the fluid channel 14 are smoothed.