To achieve calm and smooth transmission of power, achieve high transmission efficiency, and effectively prevent heat loss without causing rise of manufacturing cost.

This high speed fluid device comprises a low speed side shaft 3 provided with an outer ring 32 at one end part, and a high speed side shaft 17 eccentrically supported to the low speed side shaft 3 and the outer ring 32 to be rotatable. It also comprises a friction roller type booster A composed of one or more guide rollers 37a and 37b, and at least one movable roller 38, and using wedge action, and a high speed fluid machine X 50 connected to the high speed side shaft 17 to receive drive from the high speed side shaft 17. In a partition plate (housing) 2 around the high speed side shaft 17, a cooling water passage 70 for engine cooling water to communicate is formed.