An ejector device includes a nozzle having an inner wall surface defining a circular cross-sectional fluid passage extending from an inlet to a jet port. Furthermore, the fluid passage has a throat portion at a position between the inlet and the jet port, and a passage expanding portion in which the cross-sectional area of the fluid passage is enlarged from the throat portion as toward downstream. The passage expanding portion includes a middle portion in which the inner wall surface is expanded in a fluid flow direction by a first expanding angle, and an outlet portion from a downstream end of the middle portion to the jet port, in which the inner wall surface is expanded in the fluid flow direction by a second expanding angle that is larger than the first expanding angle. The ejector device can be suitably used for a refrigeration cycle apparatus.