To improve the rigidity and strength by providing a plastic body part making contact with a chain, a plurality of steel plate members arranged on each side surface of the body part, a plurality of connecting members for connecting the plate members to the body part.

A tensioner arm 50 comprises a plastic body part 51, a pair of plates 52, 53 mounted on the side surfaces of the body part 51. Each plate 52, 53 is formed of a steel thin plate or flat plate, and installed to the body part 51 by a plurality of pins 54-57. Each pin 54-57 is inserted and pressed into each opening 41 and 45, 42 and 46, 43 and 47, 44 and 48, respectively. This tensioner arm 50 is formed by connecting a plurality of steel plate members to the body part 51, the rigidity and strength can be improved, compared with an entirely injection molded tensioner arm.