Abstract: A cooling structure of a belt transmission for vehicles which limits the consumed power for cooling to a minimum and does not deteriorate cooling performance of the transmission. A drive pulley having a variable pitch diameter and a driven pulley which is driven through a drive belt and has a variable pitch diameter is housed in a substantially elliptical housing. An intake port formed in the vicinity of a suction part of the cooling fan formed on the drive pulley in the housing to forcedly introduce air from the outside and exhaust air to the outside. An exhaust port on the housing in a normal direction of the driven pulley at the rearward of a center of rotation of the driven pulley as seen from a side.