PURPOSE: To substantially cut by half a tensile force by forming a play between pins while setting a tab side one of holes formed on both sides of a ring plate is larger than the other, and making the pins function as a first pivot when a belt is wound around a V-shaped pulley.

CONSTITUTION: A chain belt 30 is composed of a plurality of ring plates 40, 50, pairs of rocker pins 61, 62 and 63, 64, and pairs of block pieces 71, 72. The ring plates 40, 50 have tabs 44, 45 which control longitudinal movement of a block 70 (71, 72) while a pin engagement hole of tab side is larger than that on the opposed side and specified rate of plays δ are formed between the rocker pins 61, 62 and 63, 64. When the belt 30 is wound around a V-shaped pulley, the pins 61-64 function as a first pivot 1, both blocks 71, 72 as a second pivot being a rolling face. The bending pitch is thus substantially half that of a conventional one, so is the tensile force change.