Abstract: To provide a middle point potential adjusting method for a power steering system capable of precisely equalizing a middle point potential output from a steering force detecting torque sensor to a value of a middle point potential recognized by a power steering controller. A steering force detecting torque sensor 1 is connected to a power steering controller 28 by assembling the steering force detecting torque sensor 1 in a steering force transmission path of an automobile, and a middle point potential adjusting circuit 13 is adjusted so that a torque detection signal Ts which is output from the middle point potential adjusting circuit 13 in a condition where an external force exerted to a steering handle 18 is removed is a potential C to be recognized as a middle point potential by the power steering controller 28.