To maximize the energy-conservation advantage of a system by compensating for the inside loss of a power steering load signal using a signal to which filter action is applied, providing it as an input load signal, compensating for a shift in a switching area, and changing it into a stabilized command speed signal.

The output of a sum-block 122, which is obtained from motor current, and is an approximate value of power steering load ensured for the inner loss of a system is provided in a nonlinear low-pass filter 124. The output of the low-pass filter is formed as one input to a function generator 126. The nonlinear low-pass filter 124 is formed to provide a different time constant from the changing value of power steering fluid pressure. A fast time constant is provided to increase the motor current so as to conduct switching promptly from a standby condition, and is restricted so as not to generate noise at the time of switching like this.