A xerogel production method includes: adding, to water glass, a basic silicic acid solution having a sol with a particle size between a particle size of the water glass and a particle size of colloidal silica, to acidify and solate the water glass, and polycondensing the solated water glass at 20° C. to 90° C., to obtain a hydrogel; growing the hydrogel by leaving the hydrogel for a certain time period at a constant temperature; hydrophobizing the hydrogel; and drying the hydrophobized hydrogel.