A continuously variable transmission comprising: a housing; inside the housing, a primary pulley mounted on a drive shaft and comprising a V-shaped groove of variable size to house a drive belt; inside the housing, a secondary pulley mounted on a driven shaft and comprising a V-shaped groove for the drive belt; wherein each of said primary pulley and secondary pulley comprises an axially fixed half-pulley (19A; 21B) and an axially movable half-pulley (19B; 21A) movable relative to the respective drive shaft and driven shaft, to move towards and away from each other; an actuator associated with one of said primary pulley and secondary pulley and adapted to control the axial movement of the respective movable half-pulley (19B; 21A) with respect to the fixed half-pulley (19A; 21B); wherein the actuator is connected to the movable half-pulley by means of a mechanical connection device axially extending through the fixed half-pulley; wherein the mechanical connection device comprises a variable length member; wherein the variable length member comprises a first threaded member and a second threaded member, screwed together and coaxial with the shaft (15; 17) of the pulley (19; 21), with which the actuator is associated; wherein the first threaded member is adapted to be rotated by the actuator; wherein the rotation of the first threaded member causes a change in length of the variable length member; wherein the second threaded member is axially constraint to the movable half-pulley; wherein the first threaded member has a first approximately cylindrical hollow body (71.1), characterized in that a support bearing is housed inside the first approximately hollow body (71.1), with which the first threaded member is supported rotatable on the shaft (15; 17) of the pulley, with which the actuator is associated. a housing; inside the housing, a primary pulley mounted on a drive shaft and comprising a V-shaped groove of variable size to house a drive belt; inside the housing, a secondary pulley mounted on a driven shaft and comprising a V-shaped groove for the drive belt; wherein each of said primary pulley and secondary pulley comprises an axially fixed half-pulley (19A; 21B) and an axially movable half-pulley (19B; 21A) movable relative to the respective drive shaft and driven shaft, to move towards and away from each other; an actuator associated with one of said primary pulley and secondary pulley and adapted to control the axial movement of the respective movable half-pulley (19B; 21A) with respect to the fixed half-pulley (19A; 21B); wherein the actuator is connected to the movable half-pulley by means of a mechanical connection device axially extending through the fixed half-pulley; wherein the mechanical connection device comprises a variable length member; wherein the variable length member comprises a first threaded member and a second threaded member, screwed together and coaxial with the shaft (15; 17) of the pulley (19; 21), with which the actuator is associated; wherein the first threaded member is adapted to be rotated by the actuator; wherein the rotation of the first threaded member causes a change in length of the variable length member; wherein the second threaded member is axially constraint to the movable half-pulley; wherein the first threaded member has a first approximately cylindrical hollow body (71.1), characterized in that a support bearing is housed inside the first approximately hollow body (71.1), with which the first threaded member is supported rotatable on the shaft (15; 17) of the pulley, with which the actuator is associated.