An ejector includes a body including an inflow space into which a refrigerant flows, a passage formation member disposed inside the body and having a conical shape, and a nozzle passage having an annular cross section functioning as a nozzle and a diffuser passage having an annular cross section functioning as a pressurizing portion between an inner wall surface of the body and a conical lateral surface of the passage formation member. A drive mechanism that displaces the passage formation member along a center axis is coupled to an upstream actuating bar which extends from the passage formation member toward the inflow space and is slidably supported by the body. A largest outer diameter portion of an annular member forming a wall surface of the nozzle passage provides a throat portion functioning as an edge for enlarging a passage cross-sectional area to cause a separation vortex in the refrigerant.