To efficiently adjust a flow rate irrespective of the high-low level of input side fluid pressure in an air conditioner for controlling the flow rate of piping by using a butterfly valve.

In a sealed control chamber 2, an input port 3, a vent port 4, and an output port 5a are arranged and a flapper 6 is disposed between the input port 3 and the vent port 4. A flapper displacement control unit 26 is disposed, and a variable orifice 8 using silicon rubber of small Young rate changed in inner/outer diameter by fluid pressure is disposed on the downstream side of the output port 5. Thus, flow rate adjustment of ideal characteristics is achieved within the entire adjustment range of the flow rate.