PURPOSE: To reduce dimension and weight and spread a speed change-enabled surface by fixing a concave frictional wheel having an arcuate surface on an input shaft side, installing a transmission rotary wheel through a universal joint on an output shaft side, and improving the balance of a frictional wheel type continuously variable transmission mechanism.

CONSTITUTION: A recessed arcuate surface 3 of a recessed surface frictional wheel 4 fixed on an input shaft 1 has a recessed arcuate surface having the center along the same circumference having the step difference of an output shaft 2 as radius, and the range permitting the contact with a transmission rotary wheel 5 which is inscribed with the recessed arcuate surface forms an arcuate surface ranging from the position closest to the edge of the recessed arcuate surface 3 to the position closest to the same circumference.