To improve productivity and inhibit cost increase by suppressing the number of components and to accurately control an injection quantity.

An ejector 50 includes a first and a second diaphragm 100, 110 which can displace a nozzle in an axial direction of a needle 70, and a first fluid chamber 41, a second fluid chamber 42 and a third fluid chamber 43 composed by surrounded by at least the first and the second diaphragm 100, 110. The nozzle 80 displaces by using pressure of a third fluid supplied to the third fluid chamber and can adjust a flow rate of a first fluid blowing out from an exhaust nozzle 82a by the displacement. The needle 70 includes a hollow passage 73a in which the first fluid flows at a base part 73. One side of the passage 73a communicates with the first fluid chamber 41 and another side of the passage 73a communicates with an inside of the nozzle 80 on a tip part 74 side.