To provide a device capable of perfectly damping the vibration of a playing racket, etc., for tennis, etc.

A vibration preventing device is provided with a cap 1 positioned in the periphery of a tennis racket part 2. The cap 1 is provided with a protective ring 3 formed integrally with this. The ring 3 is made from material which is not very easy to bend so that a player can easily grip the racket in his/her hand. A projection part 4 inside of this ring 3 is also formed integrally with an outer surface in the center of the end wall F of the cap 1 to constitute the vibrating part of the device. The vibrating part is provided with a cavity 5, an auxiliary weight 6 is housed there and the weight 6 is given different density to adjust vibration frequency. In addition, the flexibility of the part 4 is increased by providing opening parts 7.