PURPOSE:To enable both central control and field control of a motor by connecting a central control board and a field control box through a two core cable thereby forming a field switch self-holding line and a central control line while furthermore arranging a switching means for starting/stopping the motor on the control board. CONSTITUTION:A field control box 15 and a control board 14 are connected through a two core cable 32 and a switching means 31 for opening/closing the positive and negative polarities of an AC power source, connected respectively to the field control box 15 and the control board 14 through a diode, is arranged the control board 14. When a motor 12 is controlled by means of an operation command switch on the control board 14, central side of a changeover switch in the field control box 15 ls closed and the field side 23a thereof is opened while when the motor 12 is controlled at the field control box 15, the changeover switches 23a, 23b are operated reversely.