The present invention provides a method for manufacturing an impeller having a rotation axis as central rotation. The method has a first step of preparing a base plate, a casing, and a blade, wherein the base plate extends in a direction perpendicular to the axial direction of the impeller, the casing is disposed at one side of the base plate and is opposed to the base plate in the axial direction at an interval, and the blade is disposed between the base plate and the casing; a second step of forming an axially-extending protrusion at at least one side of an axial side and the other side of the blade; a third step of forming a through hole having a first portion and a second portion on at least one of the casing and the base plate, wherein the first portion allows the root side of the protrusion to be inserted, and the second portion allows the distal end side of the protrusion to be inserted and has a circumferential width wider than that of the first portion; a fourth step of inserting the protrusion through the through hole and inserting the blade holder between the base plate and the casing; and a fifth step of riveting the casing or the base plate and the blade.