Abstract: When a fluid flow channel is interrupted while an electronic circuit unit 50 including a microcomputer 51 and the like receives electric source power, a flow control valve is displaced to a predetermined position closer to a first end of both ends of a motion range of the flow control valve in the fluid flow channel by a stepping motor 29. When the supply of electric source power is restarted after the supply of electric source power to the electronic circuit unit 50 is stopped, a predetermined number of pulses capable of displacing the flow control valve from the first end to a home position are supplied to the stepping motor 29 to displace the flow control valve to the home position with a second end of both ends of the motion range of the flow control valve being the home position of the flow control valve.