To provide a friction transmitting device optimizing a preload between rollers according to oil temperature.

The device includes a drive roller 1 and a driven roller 2 which are pressed in contact with each other; a cam member pressed in contact with a cam follower 4a of the drive roller 1 and including a normally rotating cam 6 which generates a pressing force between both the rollers 1 and 2 in a case of normal rotation torque and a reversely rotating cam 7 which generates a pressing force between both the rollers 1 and 2 in a case of reverse rotation torque; and a preloading means 8 which gives a preload between both the rollers 1 and 2 by moving and holding both the cams 6 and 7 in a direction right-angled to the pressing force acting on a roller contact surface. The preloading means 8 increases the preload more when the oil temperature of lubricating oil high than when the oil temperature is low.