A flow controlling apparatus for a power steering system includes a variable throttle mechanism installed in the pump to change the flow rate of discharged oil from the pump to a hydraulic device; a linear solenoid mechanism controlling the variable throttle mechanism by a predetermined energizing current; a spool feeding back the excess discharged oil to a bypass passage of the pump in accordance with a differential pressure between the upstream and downstream sides of the variable throttle mechanism when the excess fluid exceeds a predetermined value; and an ECU controlling the energized current to change the transition process in accordance with a steering angular velocity of the steering wheel.