PURPOSE: To make thrust load distributable to each of paired bearings at will in an easy manner as well as to improve a span of service life in these bearings, by installing a thrust member, taking in hydraulic pressure of its own, in position between these paired bearings.

CONSTITUTION: A hydraulic pressure lead-in type thrust member 12 is installed in position between a pair of bearings 8 and 9. This thrust member 12 consists of a cylinder 10 and a piston 11. Each of these cylinder and piston 10 and 11 comes into contact with an inner rail. And, high-pressure oil in a pump or a motor is led into the thrust member 12 via a shuttle valve 7. With hydraulic pressure of this high-pressure oil, thrust load is distributed to these bearings 8 and 9. This distribution is determined on selection of the ratio of an annular area of the piston 11 to an end face area of a piston 2 of the pump or the motor.