A soundproof body comprising: one side layer formed from a porous material, an intermediate layer layered on said one side layer; and an other side layer layered on said intermediate layer so as to oppose said one side layer through said intermediate layer, wherein said intermediate layer is formed from a sound absorption layer of a membrane-vibration type which is formed from a non-air permeable thin membrane layer of a flexible material, and said other side layer is formed from a perforated sound insulation layer which is formed from a sound insulation material so as to include a plurality of opening portions in a dispersed manner, wherein an opening ratio and the number of the plurality of the opening portions of said perforated sound insulation layer are set respectively in a predetermined opening ratio range and a predetermined opening number range so as to maintain a vibration of a laminated body of said non-air permeable thin membrane layer and said perforated sound insulation layer in a predetermined phase difference range which suppresses a resonance phenomenon between vibrations of said non-air permeable thin membrane layer and said perforated sound insulation layer under masses of said non-air permeable thin membrane layer and said perforated sound insulation layer in relation to noise components of a predetermined low frequency range of noise. one side layer formed from a porous material, an intermediate layer layered on said one side layer; and an other side layer layered on said intermediate layer so as to oppose said one side layer through said intermediate layer, wherein said intermediate layer is formed from a sound absorption layer of a membrane-vibration type which is an intermediate layer layered on said one side layer; and an other side layer layered on said intermediate layer so as to oppose said one side layer through said intermediate layer, formed from a non-air permeable thin membrane layer of a flexible material, and said other side layer is formed from a perforated sound insulation layer which is formed from a sound insulation material so as to include a plurality of opening portions in a dispersed manner, wherein an opening ratio and the number of the plurality of the opening portions of said perforated sound insulation layer are set respectively in a predetermined opening ratio range and a predetermined opening number range so as to maintain a vibration of a laminated body of said non-air permeable thin membrane layer and said perforated sound insulation layer in a predetermined phase difference range which suppresses a resonance phenomenon between vibrations of said non-air permeable thin membrane layer and said perforated sound insulation layer under masses of said non-air permeable thin membrane layer and said perforated sound insulation layer in relation to noise components of a predetermined low frequency range of noise. said other side layer is formed from a perforated sound insulation layer which is formed from a sound insulation material so as to include a plurality of opening portions in a dispersed manner, wherein an opening ratio and the number of the plurality of the opening portions of said perforated sound insulation layer are set respectively in a predetermined opening ratio range and a predetermined opening number range so as to maintain a vibration of a laminated body of said non-air permeable thin membrane layer and said perforated sound insulation layer in a predetermined phase difference range which suppresses a resonance phenomenon between vibrations of said non-air permeable thin membrane layer and said perforated sound insulation layer under masses of said non-air permeable thin membrane layer and said perforated sound insulation layer in relation to noise components of a predetermined low frequency range of noise.