PURPOSE: To provide blades each having a high degree of accuracy in its area for reducing flow resistance, by integrally stacking sheet plates which are punched, in the axial direction of the pump for forming an impeller.

CONSTITUTION: Punched several thin plates 31 are integrally stacked one upon another in the axial direction of an ELMO type pump, for forming an impeller. Further, a reinforcing annular disc 32 is disposed in the middle of the impeller at the outer peripheral part thereof, and air-communication is established between the inner periphery of the disc 32 and the outer periphery of a boss 33. The thin plates 32 are made of metal plates or plastic plates in accordance with the quality of working water or the like, that is, in case of using steel plates, the tips of blades 34 are fixed together with the disc 32 for forming an integral member.