PURPOSE: To improve motor and pump efficiency by arranging a pressure room for storing a balance disk between a pump part and a motor part, and also arranging an annular balance sheet in a side edge part in a high pressure side of this balance disk, so that a design preset pressure value can be decreased by suppressing increase of a liquid pressure introduced to the motor part to realize cost reduction by simplifying a structure.

CONSTITUTION: In this constitution, an annular balance disk sheet 45 is arranged in a side edge part in a high pressure side of a balance disk 30 stored in a pressure room 32, and a flow amount of handling liquid flowing through this sheet is limited so as to reduce a pressure of circulation flow in a motor part 38.