To improve the productivity by connecting a blade member in which a plurality of blades are cut and erected on a base plate part formed of the sectional shape along an inner surface of a shell to the inner surface of the shell to secure the supporting rigidity of the blades.

An impeller comprises a shell 1 a plurality of blades 2 arranged on an inner circumference of the shell 1 with intervals in the circumferential direction, and a core 3 mounted on an inner edge of the blades 2. The blades 20 comprises a dish-shaped base plate part 21 formed of the sectional shape along the inner surface of the shell 1 and a plurality of blades 2 which are cut and erected on the base plate part 21. A plurality of connection holes 22 are formed in the base plate part 21 on the circles on the outer circumferential side and on the inner circumferential side of the cut-and-erect part of the blades 2, each projection 1a provided at the corresponding part on the inner surface of the shell 1 is fitted to each connection hole 22, and the base plate part 21 is connected to the shell 1 through caulking. In this connection method, no thermal strain is generated, different from the connection by welding, etc., and the post-machining to remove the strain can be dispensed with.