A substrate subjected to a pattern exposure process is transported to a flash bake unit. The flash bake unit performs a post-exposure bake process in which flashes of light are directed from flash lamps onto a surface of the substrate held on an upper surface of a cooling plate to momentarily heat the surface of the substrate, thereby causing crosslinking, deprotection or decomposition and the like of resist resin to proceed by using active species produced in a resist film by a photochemical reaction during the pattern exposure process as an acid catalyst, so that the solubility of only the exposed portion of the resist film in a developing solution is locally changed. The flash heating treatment performed by the irradiation with flashes of light requires extremely short treatment time of not greater than one second. This reduces the diffusion length of acid during the post-exposure bake process.