PURPOSE: To obtain a toque preference output limiter/controller for servo motor in which the low speed high torque region can be utilized through the use of a motor producing output higher than the capacity of power supply and the overcurrent error stop can be eliminated upon production of theoretically required maximum torque from a motor.

CONSTITUTION: A servo system employing a servo motor as a driving power source is provided with a controller 1 generating a speed command, a detector 5 for detecting current flowing from a speed amplifier to a servo motor, a constant output limit setter 2 for the servo motor, and an output control unit 3 for determining a target speed command being delivered to the servo motor.