Sound insulation material for vehicle and method for forming the same

A lightweight sound insulation material (10) with improved sound absorption performance and sound insulation performance and a method for forming the sound insulation material are provided. A high-density air-permeability adjustment film (12) is formed by heating and pressurizing at least a surface of a nonwoven fabric (11) including microfibers and thermal adhesive fibers. The air-permeability adjustment film (12) is made of the same material as a base material (11), and a two-layer structure including the air-permeability adjustment film (12) and the base material (11) is obtained. Thus, it is possible to improve both sound absorption performance and sound insulation performance, while achieving weight reduction.