PURPOSE: To improve the performance of a turbo-type fluid machine, by reducing the area of flow separating regions in both of a diffuser passage and an impeller passage through provision of a conduit connecting these two passages to each other.

CONSTITUTION: When a valve 12 is opened, fluid flow from a diffuser section 8 toward an impeller 3 is caused in a conduit 11 since pressure in the diffuser section 8 is higher than that in the region of the impeller 3. Here, since one end of the conduit 11 is opened on the side 7a of a guide vane 7 where the pressure is negative, i.e., in a region 14 where separation of fluid flow is caused, separated fluid is drawn into the conduit 11. Therefore, the area of the separation region 14 is reduced. On the other hand, since the other end of the conduit 11 is opened on the side 13 of the fluid passage in the casing 4, high-pressure fluid drawn into the conduit 11 from the diffuser 8 is ejected toward the impeller 3. Resultantly, energy is supplied to the fluid separated from the negative-pressure side of the impeller 3, so that the area of the separation region in the impeller 3 can be reduced.