To reduce the sliding contact resistance of a charge pump to rotate by slidingly contacting with one surface of a center section by locking a plate interposed between the center section and the charge pump on a pump case or the center section so as to be relatively nonrotatable to a charge pump case.

A plate 7 is interposed between a lower horizontal plane of a center section 5 and a side surface of a charge pump 11. In the plate 7, a delivery port 7a communicated with an operating fluid replenishing port 5c is opened in a position corresponding to a suction port of the charge pump 11. A spring is interposed between an under surface of a pump case 10 and an inside bottom surface of a half-split case 2, and presses and energizes a side surface of the charge pump 11 toward the plate 7, and an oiltight condition is held thereby. Since the side surface of the charge pump 11 rotates while slidingly contacting with the plate 7 in this condition, rolling frictional resistance of the charge pump 11 can be reduced.