To ensure sufficient durability by preventing generation of abnormal abrasion even in the case of use at high speed rotation.

A one-way clutch 37 transmitting turning force only toward an output shaft 16a from an outer ring 13a is provided between these output shaft 16a and outer ring 13a. Even when the output shaft 16a is rotated at a high speed when a center roller 24 is stopped or rotated at a low speed, the outer ring 13a is prevented from rotating at a high speed. Consequently, the above subject can be solved by preventing the external peripheral surface of each intermediate roller including a guide roller 11a and the internal peripheral surface or the like of the outer ring 13a from strongly rubbing each other.