PURPOSE: To reduce wear of a primary V belt by connecting together primary and secondary tension arms, in contact with the primary and secondary V belts respectively with a correlating spring and setting the correlating spring so as to be placed in a free length in a clutch disconnected condition.

CONSTITUTION: A primary V belt 34 is link-wound on a drive pulley 31, intermediate V pulley 33 and a transmission-upper position variable pulley 28, and a tension roller 36 in a primary tension arm 35 is adapted to the V belt 34. A secondary V belt 40 is link-wound on a driven pulley 37, secondary intermediate pulley 39 and a transmission-lower position variable pulley 29, and a tension roller 42 in a secondary tension arm 41 is adapted to the V belt 40. The primary and secondary tension arms 35 and 41 are connected by a correlating spring 48. When a clutch is placed in a disconnected condition by operating an operating arm 53, the correlating spring 48 is placed in a free length, and tension of the primary V belt disappears. Accordingly, the disconnected condition of the clutch is also sure and safe with no wear.