A coating head is constructed of a solvent feed mechanism connected to a forward side in a direction of movement of a coating solution feed mechanism, and a gas jet mechanism connected to a rearward side in the direction of movement. While moving the coating head relative to a substrate, a solvent is supplied onto the substrate from the solvent feed mechanism, then a coating solution is supplied onto a film of the solvent from the coating solution feed mechanism, and finally a gas is jetted to an uneven surface of the coating solution from the gas jet mechanism to smooth a thin film surface of the coating solution.