In the thermal spraying of powder materials, it has been observed in practice that the splat shape changes to a disk type from a splash type with increases in the substrate temperature. However, the details of the substrate surface change due to the heating has not been fully characterized. In this study, an AISI 304 stainless steel substrate surface heated to 673K was analyzed precisely by atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy. The results obtained revealed that the change of the substrate surface occurred not in the chemical composition but mainly in the surface roughness, especially surface morphology in nano-meter scale. Hence, substrate heating may bring about the change in substrate surface and this change induces the transition phenomenon.