PURPOSE: To generate large load with a small-sized device by moving a plane vane in contact with a rotating plate through viscous fluid.

CONSTITUTION: The rotatable plane vane member 27 is brought into contact with the upper surface of the rotating plate member 25 attached to an input shaft 12 through a lubricant film, and an adjusting plate rotating the member 27 through a cam mechanism (cam groove 16c) is provided above the member 27. When the input shaft 12 is rotated, viscous friction is generated between the members 25 and 21 which are rotated simultaneously, and it can be made the load. By rotating the member 27 by means of the adjusting plate, the contact area between the members 25 and 27 is changed and the magnitude of the generated load is adjusted.