A sound insulator of the invention includes a sound absorption layer 202 and an air-impermeable resonance layer 203, which are bonded to each other via an adhesive layer 204. The sound absorption layer 202 has a thickness in a range of 5 to 50 mm and an area-weight of not greater than 2000 g/m2. The sound absorption layer 202 has a two-layer structure of a high-density sound absorption layer 202a and a low-density sound absorption layer 202b, which have different densities. The high-density sound absorption layer 202a is bonded to the air-impermeable resonance layer 203 via the adhesive layer 204 and has a density in a range of 0.05 to 0.20 g/cm3 and a thickness in a range of 2 to 30 mm. The low-density sound absorption layer 202b is bonded to the other face of the high-density sound absorption layer 202a, which is opposite to the air-impermeable resonance layer 203, via an adhesive layer 202c and has a density in a range of 0.01 to 0.10 g/cm3 and a thickness in a range of 2 to 30 mm. The structure of this sound insulator effectively reduces a noise level in a voice-tone frequency band, especially in a high frequency domain, thereby efficiently enhancing the clarity of conversion in a vehicle interior.