PURPOSE: To surely prevent an arm from its falling naturally, by turning the gate of an amplifier with a gate function OFF after a brake for fixing an arm being actuated really.

CONSTITUTION: In the case of stopping a robot, a brake 8 is turned ON simultaneously with turning a servo power source 7 OFF first. At this time the servofunction is operating because the gate function of an amplifier 3 is not turned OFF yet, so an arm is not dropped naturally even in case of the function of the brake 8 not functioning actually at the time of this state. Thereafter, the gate function is turned OFF, after the lapse of the specified set time spent for the actuation start of the brake 8. After this time, the arm does not fall naturally even in case of the servofunction being turned OFF with the gate function being turned OFF, because of the function of the brake 8 functioning actually.