Two-stage decompression ejector and refrigeration cycle device

A two-stage decompression ejector comprising:

• a variable throttle mechanism including a first throttle passage configured to decompress and expand a fluid and a valve body configured to change a throttle passage area of the first throttle passage;
• a nozzle having therein a second throttle passage, the second throttle passage being adapted to further decompress and expand the fluid decompressed by the variable throttle mechanism;
• and
• a suction portion configured to draw a fluid by a suction effect of a jet-flow fluid ejected at a high velocity from the nozzle,
• wherein the following formula is satisfied:
• 0.07≦Vo×S/vn≦0.7
• where Vo is an intermediate-pressure space volume (mm3) that is a volume from an outlet of the variable throttle mechanism to an inlet of the second throttle passage, S is a throttle passage area (mm2) that is a passage sectional area of a minimum passage sectional area portion of the second throttle passage, and vn is a flow velocity (mm/s) of the fluid passing through the minimum passage sectional area portion.