PURPOSE: To further improve responsiveness even if the difference in rotating speed between both plates is slight by providing an interval adjusting device which moves either of inner and outer plates with respect to the other in the axial direction and reducing the interval between both plates.

CONSTITUTION: In order to improve the transmission of torque, an actuator 40 is operated extending a rod 40a, a lever 42 is swung in the B direction pressing thrust washers 24, and a housing 20 is moved axially in the A direction via spline parts 28a and 29a, thereby, reducing the intervals between inner plates 10 and outer plates 21. Thus, as the intervals between the plates 10 and 21 are reduced, a shearing stress applied to a viscous fluid 3 in a closed space 22 is accompanyingly increased, thereby, enabling a torque transmission in inverse proportion to the dimension of the interval. The transmission of torque can be also carried out by closely attaching the plates 10 and 21 in a directly connected condition. Accordingly, the response performance of a viscous clutch can be improved.