To provide a centrifugal pump having an impeller capable of generating equilibrium of the thrust force acting on the impeller from ahead thereof and behind.

The impeller 26 of the centrifugal pump is furnished with a back face wear ring 44 having a greater diameter than a front face wear ring 40, wherein a thrust adjusting window 48 is provided in a back face shroud 38. The thrust PBAB acting from the back face is put in equilibrium with the thrust PSAS acting from the front face by adjusting the area AB whereon the pressure PB acts through adjustment of the area of the thrust adjusting window 48.