PURPOSE: To provide an opening/closing mechanism which easily prevents the generation of chattering, and permits the easy assembly, and realizes the cost reduction of parts.

CONSTITUTION: The first and second arms 2 and 3 are installed in turnable manner son a shaft 1, and the first and second turning plates 4-8 which are installed in turnable manner on the shaft 1 are engaged or fixed an the first and second arms 2 and 3, and the arm and the turning plate are closely attached by a belleville spring 9 and a bush nut 10. Each turn of the first and second arms 2 and 3 is suppressed by the frictional force generated between the first and second turning plates 4 and 8 which are closely attached with the first and second arms 2 and 3, and the first and second arms 2 and 3 are stopped at a prescribed position relation.