An inertia damper has a mounting base (10) to be mounted on a rotary shaft (40) and an inertia weight component (20) which is coupled to the mounting base through a vibration absorbing layer so the vibration absorbing layer being made of a gel material with a penetration value of approximately 50 to 200. The inertia weight component is adhered to one surface of the vibration absorbing layer and the other surface of the vibration absorbing layer is adhered to the mounting base of the rotary shaft. A vibration wave generated at the rotary shaft side is dispersedly absorbed by deformation of gel material which forms the vibration absorbing layer and a vibratory component can be removed from a braking motion.