PURPOSE: To make stable and high precision contact of both a driven roller and a center roller by putting a turnable eccentric bush between the driven roller and a revolution support shaft, and mounting a pressure ring and a fixing ring having the tapered faces in contact with the driven roller and setting a means which gives pressure axially to the pressure ring from the input side.

CONSTITUTION: If a driven roller 7 makes uneven contact with a center roller 6 since the accuracy of the pitch circle of a revolution support shaft 8 is unsatisfactory or the center point of this pitch circle is offset from the axis of the output turning shaft is, the pressure member 21 of a pressure means presses a pressure ring 20 toward a fixed ring 19. By this pressure the driven roller 7 is forced to make contact with the opposing tapered surfaces 19a and 20a which are the internal surfaces of the pressure ring 20 and the fixed ring 19, to press them toward the center roller 6, whereby automatically turn an eccentric bush 9 which turnably receives the revolution support shaft 8. The eccentric position thereof may be corrected to have both the driven roller 7 and the center roller 6 make contact with each other under even pressure.