PURPOSE: To achieve the cut down of the number of parts and the reduction of assembling manhour by making a mechanical contact switch or a sensor needless, in a motor automatic driving device for operating or stopping a motor, according to the existence of load.

CONSTITUTION: This driving device is equipped with a current detecting means 2, which detects the current flowing in a motor 11, a voltage detecting means 3, which detects voltage, an operating means 6, which calculates power by multiplying the current by the voltage, a comparison means 7, which outputs an operation signal when the value to show the power gets over the preset value and outputs a stop signal when the value to show power is below the preset value, a control means 8, which outputs an operation signal when the motor 11 has maintained in the stop condition for a certain time, and a power switching means 9, which operates or stops the motor 11, according to an operation signal or a stop signal.