PURPOSE: To eliminate necessity for a torque cam collar by forming a torque cam groove on an external surface of a rotary shaft, in the case of a speed change gear provided with a torque cam mechanism for generating thrust in a direction of closing a pulley by relative rotation between a movable sheave and the rotary shaft in the speed change pulley.

CONSTITUTION: A speed change pulley 6 having flange-shaped fixed/movable sheaves 7, 8, opposed to each other, is supported to a point end part of a rotary shaft 1 in a drive side, to link a V belt B wound to a belt groove 12 of V-shaped section partitioned between both the sheaves 7, 8. A cam mechanism 16 for bringing the movable sheave 8 near to and separating it from the fixed sheave 7 is provided in a back surface side of the movable sheave 8 of the speed change pulley 6, and this cam mechanism has a cylindrical cam 18 rotated about the rotary shaft by operating a turning lever 20. Here, a pair of helical torque cam grooves 9 are formed on the periphery of a sleeve 4 to which a boss part 8a of the movable sheave 8 of partly constituting the rotary shaft 1 is impulse-movably supported, and torque pins 11 fixed to the boss part 8a are engaged with each cam groove 9.