In an ejector, a substantially conical passage formation member is disposed in the interior of a body forming a space therein to define a nozzle passage functioning as a nozzle, a mixing passage in which an ejection refrigerant ejected from the nozzle passage and a suction refrigerant drawn from a suction passage are mixed together, and a diffuser passage that converts a kinetic energy of the refrigerant that has flowed out of the mixing passage into a pressure energy, between an inner peripheral surface of the body and the passage formation member. The passage formation member is configured so that a spread angle of a portion forming an outlet side of the nozzle passage is smaller than a spread angle of a portion forming an inlet side of the nozzle passage in a cross-section parallel to an axial direction of the passage formation member.