PURPOSE: To smoothly reduce the delivery rate to a power steering apparatus to stabilize the steering operation by allowing a spool to move in the same direction following the movement of a delivery rate control valve when the delivery fluid pressure from a pump exceeds a predetermined value.

CONSTITUTION: When the pump speed is increased at high vehicle speeds, a delivery rate control valve 2 slides to the left to oepn a return port 1c, and a throttle passage 8 is formed between the large diameter part of a rod 7 and a throttle hole 5a. If steering is performed under such condition, a loading pressure inside a power steering apparatus is increased, and such a pressure moves the delivery rate control valve 2 to the left through passages 4b, 1e, 1f. Although the rod 7 moves to the left to increase the area of opening of the passage 8, the area of the opening will not change as the delivery rate control valve 2 throttles the return port 1c to increase the pressure inside an oil supply port 1b to cause a spool valve 5 to move to the left similarly to the movement of the rod 7. Therefore, the oil supply is always maintained to be constant.