To provide a coating agent for glass suitable for on-site construction.

A method for producing a coating agent for glass, which forms an inorganic layer of inert transparent ceramics on the surface of glass, includes: mixing a peroxotitanic acid aqueous solution and an alcoholic aqueous solution to produce a peroxotitanium-containing alcoholic aqueous solution; mixing lithium silicate and an alcoholic aqueous solution to produce a lithium silicate-containing alcoholic aqueous solution; and then mixing the peroxotitanium-containing alcoholic aqueous solution, the lithium silicate-containing alcoholic aqueous solution, and a polyoxyethylene ether containing a short-chain perfluoroalkyl group to produce a coating agent for glass containing the peroxotitanic acid aqueous solution and the lithium silicate.