The present invention relates to a core for an insulation material, a manufacturing method therefor, and a slim insulation material using the same. The core for an insulation material according to the present invention comprises a plurality of micropores, capable of trapping air, by stacking multiple layers of a three-dimensional nano-web obtained by electrospinning a polymer material having low thermal conductivity, and using the stacked nano-web layers as core materials. Accordingly, the core for an insulation material according to the present invention is thin but has excellent insulation efficiency. The core for an insulation material according to the present invention comprises a porous nano-web, wherein the porous nano-web is made of a polymer having low thermal conductivity and has a three-dimensional micropore structure in which nano-fibers, having a diameter less than 3 , are spun and integrated.