To provide a fitting structure of a dynamic damper in which the space required for installation is reduced while appearance in a wheel house is good, with its performance maintained without maintenance.

A dynamic damper 1 comprises a base 2 which is so fitted to an upper surface 115 of a fitting part 117 as to stride over a recess 122 of the fitting part 117 of a spring bracket 114, a mass 3 fitted inside the base 2 through a rubber 10, and a cover 4 fitted to the upper surface 115 of the fitting part 117 through the base 2. Related to the base 2, an opposed part 22 facing the recess 122 is bent upward. The mass 3 is fitted inside the opposed part 22 so that it is positioned in a space 12 formed with the recess 122 and the interior 23 of the opposed part 22 when the base 2 is fitted to the upper surface 115 of the fitting part 117. The cover 4 is so formed as to cover the recess 122 of the fitting part 117 as well as the base 2.