To provide a planetary roller power transmission device which can suppress heat generation and abrasion at a contact part of a roller side surface by a simple means.

In a multistage roller transmission device, at least two kinds of roller groups are arranged in a space formed between a sun roller and an outer ring concentrically arranged on its outer peripheral side, in a multistage and pressure contact state. In addition, at least one of the roller group is made up of planetary rollers provided with outer peripheral surfaces having different radii of rotation. In such a multistage roller transmission device, a planetary roller 23, having outer peripheral surfaces of different radii of rotation, is composed of a small diameter part 33 and a large diameter part 34 arranged on both sides thereof and provided with a flange surface 35 on its axially inner side. Axial clearance is formed between a side surface of the planetary roller frictionally contact with the small diameter part 33 and the flange surface 35 of the large diameter part 34 of the planetary roller. The axial clearance is gradually increased toward a radially outward direction of the planetary roller 23.