To place an electric motor, which composes a groove width adjustment mechanism, away from a heat source so that the electric motor can be cooled actively, and to improve both the protection and the maintainability of the electric motor.A primary sheave 113 and a secondary sheave 123 each forming a V-groove with a variable width for receiving a belt are provided. A case 105 for housing the primary sheave 113 and the secondary sheave 123 is formed with an opening 110 for sucking and exhausting air into and out of the case 105. An electric motor 140 for driving a groove width adjustment mechanism 141 for the V-groove of the primary sheave 113 is disposed in an airflow path outside the case 105.