To provide an automatic operating device for an electric pump in which in the electric pump using a three-phase induction motor as a prime mover, current flowing in an opening/closing mechanism incorporated in an electric circuit for operation control is reduced, the opening/closing mechanism having small contact capacity is compactly formed, one opening/closing mechanism is used both for controlling automatic operation of the pump and protecting burnout of the motor, the pump is reduced in weight and miniaturized by reducing storage space, and a liquid level sensor effectively functions even in nonconductive liquid.

A control device 5 for controlling operation of the electric pump based on a signal from a temperature sensor 3 detecting abnormal heat generation of the three-phase induction motor 2 or the liquid level sensor 4 detecting a liquid level, and the opening/closing mechanism 6 for opening/closing delta connections of motor windings 2c, are incorporated in the electric circuit for controlling operation of the pump. The opening/closing mechanism 6 is composed to have both the functions of protecting burnout of the motor 2 and controlling automatic operation of the pump. The liquid level sensor 4 is a photoelectric liquid sensor.