A new surface modification method “laser quenching after coating” using a high power diode laser equipped with a 2-dimensional galvano-scanner unit was developed to process a larger area of ceramic coated steel uniformly and efficiently. The laser irradiation tests for 3 kinds of ceramic-coated steels: CrAlN, TiAlN and CrN, were carried out with the scanning laser, and the appropriate irradiation conditions to achieve the uniformly quenched substrate without any surface damage were clarified for these ceramic-coated steels. The area of the substrate surface wider than the laser spot size could be easily quenched by the scanning laser. The adhesive strength, the film hardness of the laser-irradiated regions and the deformation caused by laser irradiation were evaluated. Laser quenching with the scanning laser can effectively improve the adhesive strength and substrate hardness without any detrimental effect on the film hardness of the ceramic-coated specimens. In the deformation of the laser-irradiated specimens, two features were recognized; one is the bending, and the other is the expansion of laser-irradiated part. It was found that the deformation of ceramic-coated steel by laser irradiation under the same heat input condition does not depend on the kind of ceramic thin film but on the steel type of the substrate. It was concluded that “laser quenching after coating” with scanning laser could easily improve the adhesive strength and substrate hardness without any detrimental effect on the film hardness of large surface areas in the tested all types of ceramic-coated specimens.