Used is a method for producing a thermal insulation sheet, including: composite-forming including impregnating a nonwoven fabric with a basic sol prepared by adding a carbonate ester to a water glass composition to form a hydrogel-nonwoven fabric composite; surface-modifying including mixing the composite with a silylating agent for surface modification; and drying including removing liquid contained in the composite through drying at a temperature lower than the critical temperature of the liquid under a pressure lower than the critical pressure of the liquid. Used is a thermal insulation sheet including an aerogel and a nonwoven fabric, where the thermal insulation sheet exhibits a compressibility of 40% or lower at 0.30 to 5.0 MPa.