To provide a dynamic damper which can be used without worrying about degradation of safety or appearance aggravation and has enough relaxation/reduction actions against impulsive vibration.

The appearance aggravation is prevented by employing a side spreading structure whole of which is hard to stand out wherein a viscoelastic material 2 thin thickness and a thin weight addition material 3 are unitized by connecting face to face, and on the other hand the degradation of safety is prevented by going without a person having a pain or a cutting when hit by imparting softness to the weight addition material 3 with a high molecular matter being impregnated therein and by giving enough deformability to the viscoelastic material 2 with complex modulus of elasticity thereof being set as 1.5 MPa or less and with thickness thereof being set as 2.5 mm or greater, and further the relaxation/reduction actions against impulsive vibration are fully demonstrated by allowing full resonance phenomena to occur with the viscoelastic material 2 not being powerfully restricted by the weight addition materials 3.