PURPOSE: To make it possible to change the amount of converted motion and the direction of motion by providing a rotating shaft, an outer ring concentric thereto, a planetary roller which supported on both ends by a pair of retainers respectively and make rolling contact with outer peripheral surface of the rotating shaft and inner peripheral surface of the outer ring and a retainer adjusting member.

CONSTITUTION: A planetary roller 2 is given a skew angle by making the axial direction of the planetary roller 2 non-parallel to the axial direction of a rotating shaft 1 and an outer ring 3 through rotating one retainer 4 around the rotating shaft 1 of the other retainer with an adjusting member 5. Then, in a case when the planetary roller 2 acts as input part and the rotating shaft 1 acts as output part, the rotating shaft 1 is rotatingly driven around the axis thereof and at the same time, given a thrustwise drive force, makes a linear motion, too. And rolling contact between the planetary roller 2 and the rotating shaft 1 generates thrustwise drive force in proportion to the skew angle of the planetary roller 2 between the rotating shaft 1 and the planetary roller 2, thereby changes an amount of linear motion of the rotating shaft 1 per one rotation of the planetary roller 2.