PURPOSE: To show damper effect to aim at improvement of performance stability by providing a locking means on the outer circumference of a cylindrical member and molding synthetic resin by injection the outside thereof in an automatic tensioner for regulating the tension of a timing belt, etc. of an automobile.

CONSTITUTION: A synthetic resin made bush 15 is fixedly provided at the circumference of the bush formed face 11e of a fixing member 11. A bush 15 is formed by applying knurling machining to the bush formed face 11e and forming synthetic resin by injection on the face 11e. Rotation between the fixing member and the bush is securely prevented. Thus, damper effect is shown at a place between the bush and an eccentric member so that improvement of its performance stability can be attempted.