PURPOSE: To provide a centrifugal fluid clutch which has no converting shock, and can maintain the frequency of an outer ring constant regardless of the frequency of an input shaft.

CONSTITUTION: A vane pump 32 rotated by the difference of the relative frequencies of an input shaft 1 and an output outer ring 2 between both members is provided, a communicating passage of the discharge opening 34 and the suction opening 33 of the vane pump 32 is provided on the output outer ring 2, and a centrifugal control valve 23 to open and close the communicating passage 35 according to the value of the centrifugal force is provided on the output outer ring 2, so as to compose this centrifugal fluid clutch.