The present invention relates to a method for manufacturing a low density inorganic powder insulator having a low density molded structure using expanded perlite without a binder and a mold machine for manufacturing the same, and more particularly, to a technology of uniformly dispersing perlite particles having a shape of irregular fragments of glass using expanded perlite to form a framework among synthetic silica to improve molding strength even at a low density, thereby reducing thermal conductivity (conduction and convection blocking) due to a low density and an increase in a specific surface area. Further, the present invention relates to a method for manufacturing a low density inorganic powder insulator having a molded structure using economical expanded perlite having excellent physical properties by compression-molding a clad sheet material using a mold machine having a porous plate and a filter so as to remove pressure and air, which are generated during compression due to the use of the clad sheet material having low specific gravity and a large specific surface area, from a molded product or manufacturing the clad sheet material into a compressed clad sheet using a compression roller, and a mold machine for manufacturing the same.