PURPOSE: To provide a sound absorbing material which does not provide an uncomfort able feel when touched by an operator, is hardly breakable in spite of application of load thereon, is not deteriorated by humidity, etc., has a long pot life, makes it possible to obtain a desired shape, maintains the initial shape without changing over a long period of time and is short in the working time required for molding.

CONSTITUTION: A stampable sheet formed by mixing a thermoplastic polypropylene(PP) resin and glass fibers is preheated to be expanded and to be provided with air permeability. This preheated sheet is held by two metal molds and is cooled to fix the shape to the shape of the sound absorbing material 1 consisting of leg parts 3 fixed to a wall surface 2 and a sound absorbing wall 5 forming a rear air layer 4 with the wall surface 2. The circumference is thereafter cut, by which the sound absorbing material 1 is formed. The sound absorbing material 1 allows incident of sound waves on the inside of the rear air layer 4 to attenuate approximately the max. particle velocity of the sound waves. The wavelength of the sound waves to attenuate the particle velocity changes with this sound absorbing material 1 as the incident angle changes. Since the sound absorbing material 1 is the composite of the PP resin and the glass fibers, the purposes described above are attained.