The motor control system of the present invention includes a signal receiving unit for receiving a signal for operating a mechanical brake, a position monitoring unit for obtaining the history of the rotational position of the servo motor from the receipt of the signal to when the rotation of the servo motor stops using a position detector, a displacement amount calculation unit which calculates the rotational displacement of the servo motor from the receipt of the signal to when the rotation of the servo motor stops from the history, and an abnormality determining unit which determines that an abnormality exists in the mechanical brake when the calculated rotational displacement exceeds a predetermined first threshold value.