To reduce engine noise and shut-up noise with a simple structure.

A sound absorbing material 22a attached to the vehicle room 2 side of a toeboard 8 consists of a low density felt, and a sound absorbing material 22b provided on the surface of the sound absorbing material 22a consists of a high density felt having a gas permeability, and a sound absorbing material 21 is attached to the back of an instrument panel 11 arranged above the toeboard 8. The toeboard 8 and the instrument panel 11 surround a space 12, which is enclosed with the sound absorbing materials 22a, 22b, and 21. As a result, engine noise passing through the toeboard 8 is absorbed by the sound absorbing materials 22a, 22b, and 21, where the engine noise is not reflected at a toeboard insulator 22 but is absorbed in the sound absorbing materials 22a, 22b, since the surface skin of the toeboard insulator 22 consists of the sound absorbing material having a gas permeability. Also, with the surface skin made of the sound absorbing material 22b of the high density felt, the weight of the soundproof structure can be reduced, the resonance of the toeboard insulator 22 in a low frequency can be avoided, and the deterioration of the sound insulating capability of the soundproof structure can be avoided. Further, one end of the vehicle room becomes a non-reflective end, so that noise shut up in the vehicle room can be reduced.