The present invention relates to an insulation used in home appliances and building materials. A method of manufacturing an insulation includes fabricating an adhesive solution by inputting a binder to water contained in a water tank, inputting long glass fibers to the adhesive solution, removing moisture by supplying the long glass fibers to a mesh belt, wherein the mesh belt move left and right and front and rear so that the long glass fibers are uniformly spread, fabricating glass fiber paper by drying the long glass fibers, winding the glass fiber paper in a roll form, and preparing the glass fiber paper rolls in multiple layers, stacking two or more sheets of the glass fiber paper supplied from the rolls, and sewing the sheets of stacked glass fiber paper.