A continuously variable transmission device including a guiding cover rotating about a first axis, a guided cover rotating about a second axis, a planet gear including a first belt in contact with an inner surface of the guiding cover and a second belt in contact with an inner surface of the guided cover, contact areas between the belts and the inner surfaces of the covers being defined in a single first radial plane relative to the first axis, wherein the planet gear rotates about a third axis contained in the first radial plane, the angular orientation relative to the first axis defining the transmission ratio of the device, and wherein the planet gear pivots about a fourth axis perpendicular to the first radial plane and nonintersecting with the first axis, and pivots about a fifth axis parallel to the first radial plane and perpendicular to the third axis.