PURPOSE: To execute the working of exact positioning with the zero positioning error quantity of the shaft of an NC (numerical control)machine tool or the like, by adding a torque command value and a retaining torque command value to each other, and by finding a current command value.

CONSTITUTION: At a retaining torque computing section 21, the driving system weight of an object shaft requiring constant retaining torque is multiplied by gravitational acceleration. Then, a retaining torque command value SKT according to the multiplied value is found based on a previously commanded retaining torque computing data. By a torque command adding section 22, a torque command value ST from a speed controlling section 6 and the retaining torque command value SKT from the retaining torque computing section 21 are added to each other, and a torque command value SAT is found, and the input to a current command computing section 7 is provided.