PURPOSE: To improve pumping efficiency of multi-phase fluid of high vapor-liquid rate by setting the number of rotary blades to the plural number and by constituting the cross section of the blades in the right radial direction in such a state as satisfying a specific equation in a device compressing the multi-phase fluid composed of a liquid phase and a gaseous phase.

CONSTITUTION: Major parts of a device body are composed of a housing 1, and an impeller having a suction part 41 and a discharge part 42. The impeller is formed out of a shaft 6 and an axial-symmetry hub 28 having n-blades rotating about the shaft. A plurality of front edges C1, C2 and rear edges C2', C2' are arranged in respective blades. After the fluid flows from the intake part 41 into the impeller, it is discharged from the discharge part 42. On the other hand, the number of the rotary blades 29, 30 is set to 2 or more than 2. Where, the cross section in the right radial direction of the blade is at least a part of the length and regulates at least a conduit by two continuous blades having a shape of 5%-3% of that expressed by an equation: S(x)=ax2+b(c-x2)1/2+d.