A continuously variable transmission mechanism that changes a transmission ratio, comprising: a set of two composite sprockets (5, 5) each having: a rotation shaft that inputs or outputs power; a plurality of pinion sprockets, each of which is supported movably in a radial direction with respect to the rotation shaft; and a sprocket movement mechanism that moves the plurality of pinion sprockets in the radial direction in synchronization with each other while maintaining equidistance of each of the pinion sprockets from a shaft center of the rotation shaft; a chain wound around the set of two composite sprockets (5, 5), the transmission ratio being changed by changing a circumcircle radius that is a radius of a circle that encircles all of the plurality of pinion sprockets and circumscribes all of the plurality of pinion sprockets; and a mechanical rotation drive mechanism (50; 150) mechanically driving rotation of at least one rotation pinion sprocket (22; 23) on its axis from among the plurality of pinion sprockets in concert with the sprocket movement mechanism, characterized in that the sprocket movement mechanism has a sprocket supporting shaft (21 a, 22a, 23a) that supports the pinion sprocket; a stationary disk that is provided with a sprocket stationary radial slot (11 a), in which the sprocket supporting shaft (21a, 22a, 23a) is fitted, and rotates integrally with the rotation shaft; a movable disk that is disposed concentrically with the stationary disk, can rotate relatively to the stationary disk and is provided with a sprocket movable radial slot that intersects the sprocket stationary radial slot, the sprocket supporting shaft (21 a, 22a, 23a) being positioned in an intersection position between the sprocket movable radial slot and the sprocket stationary radial slot; and a drive mechanism that drives relative rotation of the movable disk with respect to the stationary disk and moves the intersection position in the radial direction. a set of two composite sprockets (5, 5) each having: a rotation shaft that inputs or outputs power; a plurality of pinion sprockets, each of which is supported movably in a radial direction with respect to the rotation shaft; and a sprocket movement mechanism that moves the plurality of pinion sprockets in the radial direction in synchronization with each other while maintaining equidistance of each of the pinion sprockets from a shaft center of the rotation shaft; a rotation shaft that inputs or outputs power; a plurality of pinion sprockets, each of which is supported movably in a radial direction with respect to the rotation shaft; and a sprocket movement mechanism that moves the plurality of pinion sprockets in the radial direction in synchronization with each other while maintaining equidistance of each of the pinion sprockets from a shaft center of the rotation shaft; a chain wound around the set of two composite sprockets (5, 5), the transmission ratio being changed by changing a circumcircle radius that is a radius of a circle that encircles all of the plurality of pinion sprockets and circumscribes all of the plurality of pinion sprockets; and a mechanical rotation drive mechanism (50; 150) mechanically driving rotation of at least one rotation pinion sprocket (22; 23) on its axis from among the plurality of pinion sprockets in concert with the sprocket movement mechanism, characterized in that the sprocket movement mechanism has a sprocket supporting shaft (21 a, 22a, 23a) that supports the pinion sprocket; a stationary disk that is provided with a sprocket stationary radial slot (11 a), in which the sprocket supporting shaft (21a, 22a, 23a) is fitted, and rotates integrally with the rotation shaft; a movable disk that is disposed concentrically with the stationary disk, can rotate relatively to the stationary disk and is provided with a sprocket movable radial slot that intersects the sprocket stationary radial slot, the sprocket supporting shaft (21 a, 22a, 23a) being positioned in an intersection position between the sprocket movable radial slot and the sprocket stationary radial slot; and a drive mechanism that drives relative rotation of the movable disk with respect to the stationary disk and moves the intersection position in the radial direction. a sprocket supporting shaft (21 a, 22a, 23a) that supports the pinion sprocket; a stationary disk that is provided with a sprocket stationary radial slot (11 a), in which the sprocket supporting shaft (21a, 22a, 23a) is fitted, and rotates integrally with the rotation shaft; a movable disk that is disposed concentrically with the stationary disk, can rotate relatively to the stationary disk and is provided with a sprocket movable radial slot that intersects the sprocket stationary radial slot, the sprocket supporting shaft (21 a, 22a, 23a) being positioned in an intersection position between the sprocket movable radial slot and the sprocket stationary radial slot; and a drive mechanism that drives relative rotation of the movable disk with respect to the stationary disk and moves the intersection position in the radial direction.