To carry out a number of restrictive amounts at once with remote controlling by arranging a restrictive amount control part which varies a restrictive amount based on an electric signal to be input.

A first control mechanism 50a displaces a valve element 52 so as to approach a valve seat 54, while a second control mechanism 50b displaces the valve element 52 so as to be spaced from the valve seat 54. A first solenoid valve or a second solenoid valve is energized and deenergized by electic signals output from a controller. A spacing between the valve element 52 and the valve seat 54 can easily be varied through the first control mechanism 50a and the second control mechanism 50b driven by the first solenoid valve or the second solenoid valve 50b. Maintenance operation is facilitated by electrically controlling a restrictive amount. A number of speed controllers 10 connected to the controller can be adjusted in restrictive amounts at once with remote controlling.