PURPOSE: To decrease the tooth striking noise by furnishing viscous damper mechanism between a plurality of flywheels, fitting the driven plate of this damper mechanism on the boss part of one of the flywheels by means of contractive fit, and thereby maintaining the gap between them at the minimum.

CONSTITUTION: A power transmitting device is composed of a flywheel assembly 101, clutch disc 102, and clutch cover assembly 103, wherein the flywheel assembly 101 consists of a plurality of flywheels 1, 2 and a viscous damper mechanism 3 installed between them. A rolling bearing 4 is installed on the boss part of one of the flywheels 1, and at its periphery a ring-shaped boss member 5 is furnished to which the other flywheel 2 is secured. Therein internal circumferential serration is formed at the driven plate 9 of the damper mechanism 3, while outside serration is formed at the boss member 5 to be fitted in the internal serration contractively.