A steering force control apparatus for a power steering system includes a valve. The valve includes a valve hole, a spool, and a spring. A main pump oil supply path branched from a main hydraulic path extending from a pump to a power cylinder, a reaction path connected to a hydraulic reaction chamber, and a discharge path connected to a tank are open to the valve hole to be spaced apart from each other by predetermined distances along an axis of the valve. The spool is slidably arranged in the valve hole and has land portions so as to change connecting states of the main pump oil supply path, the reaction path, and the discharge path. The spring always biases the spool in one direction. A subpump oil supply path for supplying a fluid from a subpump whose delivery pressure is changed is connected to an end of the spool which is biased by the spring, thereby controlling an operation of the spool by the subpump in correspondence with a vehicle speed.