To enable uniform coating without excessively using a transparent coating agent on a glass plate on the execution site by using sponge having specified number of cells, elongation and hardness in the coating with a coating agent.

When a transparent coating agent is applied to a glass plate, sponge with a number of cells of 30-25mm or more, an elongation of 200% or more and a hardness of 5kgf or more is used in the application of the coating agent. The coating instrument used in this coating method is constituted of a substrate 1, a support member having at least one sponge support plate 4 provided between both side plates 2, 3 and the sponge for applying the coating agent and the upper surface of the sponge upwardly protrudes from the upper surface of both side plates 2, 3 and attached to a sponge support plate 4 by notches provided in the rear surface thereof. As the sponge material, a property insoluble in an org. solvent is required and natural sponge can be used but, in a usual case, synthetic resin type open-cell foam is used.