To provide a traction transmission device contributive to reducing its size and cost by adjusting the traction property of a contact face relating to transmission without using a continuously variable transmission and a transmission control device at start, stop or a speed change such as acceleration or deceleration.

In the traction transmission device, rotation given to a high speed shaft 2 is transmitted to a sun roller 5 to revolve and rotate a planetary roller 8 on the inner peripheral face of a ring 11 and the revolution of the planetary roller 8 is only transmitted from a bearing 12 via a carrier 13 to a low speed shaft 14. Normal force is given to the contact face by a plate spring 10 and a cam mechanism. In normal operation, contact bearing pressure is set to be consistently 1 GPa or lower so that slight slippage is allowed to relax impact at a speed change such as acceleration or deceleration and the cam mechanism is operated at emergency stop.