The operation state of a servo motor is monitored and output to a user before automatic termination of power to the motor. A servo system includes a servo motor and a safety unit. The safety unit cuts off electric power to the servo motor when at least one of a speed, a position, acceleration, an amount of movement, a movement direction, and torque of the servo motor is outside a first operation range. Furthermore, the safety unit outputs a warning when at least one of the speed, the position, the acceleration, the amount of movement, the movement direction, the torque is within the first operation range, but is outside a second operation range that is narrower than the first operation range. User controls allow reduced operation when outside the second operation range.