An ejector includes a nozzle portion and a body portion. A suction port, a mixing portion, and an outlet are formed in the body portion. The mixing portion includes a tapered mixing portion and a divergent mixing portion. The tapered mixing portion accelerates a velocity of mixed fluid to a value equal to or higher than a speed of sound. The divergent mixing portion generates a shock wave in the mixed fluid flowing out of the tapered mixing portion and eliminates the generated shock wave. The tapered mixing portion forms a fluid passage having a shape with a passage cross-sectional area reduced in the flow direction of the mixed fluid. The divergent mixing portion forms a fluid passage having a shape with a passage cross-sectional area increased in the flow direction of the mixed fluid.