Abstract: It is an object of the present invention to obtain the configuration in which sound transmission can be decreased and sound insulation property can be enhanced in a double wall structure as an automobile part such as a door, a hood, and a truck lid. In a double wall structure in which an internal space 4 is formed between facing plate-like bodies 2 and 3 and the internal space 4 is closed, at least one sound absorbing material 6 which reduces an air particle speed is provided at a position where the air particle speed is maximum in the internal space 4 or near the position. As the sound absorption material 6, a porous body, a plate-like body, a foil-like body, and a film-like body (including the material having many through holes) can be adopted. The sound absorbing material 6 is in contact with at least one of excitation-side plate-like body and radiation-side plate-like body in the facing plate-like bodies 2 and 3.