PURPOSE: To enable to conduct the sound-insulating treatment easily while maintaining the vehicle body in normal position regardless of the locations of the objective part to be treated, by a method wherein a heat-fusible damping sheet is pressure contacted to the objective part of the vehicle body by a sheet formed of magnetic material and then the damping sheet is fused to the objective part.

CONSTITUTION: The heat-fusible damping sheet 1, a polyester film 3 and the sheet formed of magnetic material 2 are sequentially laid on the objected part such as a top 4 of the vehicle body, whereby the damping sheet 1 is pressure contacted with the top 4. In this condition, a heat treatment is conducted within a predetermined temperature range to fuse the damping sheet 1 to the top 4, and after cooling, the magnetic material 2 and the polyester film 3 are removed. Accordingly, the damping sheet can be easily fitted to the objective part while maintaining the vehicle body in normal position regardless of the location of the objective part.