To provide an impeller for a pump dispensing with filling resin in a recess counterbored in a plate face of a rotary disk (a shroud) for weight balance adjustment.

An annular masking plate 6 is fixed overlapped with the plate face of the rotary disk (shroud) 1 to close a plurality of recesses 5 counterbored in the plate face of the rotary disk (shroud) 1 for the weight balance adjustment of the impeller. Filling of resin into the recesses 5 counterbored in the plate face of the rotary disk (shroud) 1, and chipping work for a swollen part after filling are dispensed with.