In this paper, we discuss the development of an inspection system for a gloss-coated surface using patterned illumination. The convex defect on a gloss-coated surface is caused by top-coating paint on a primary coating with minute particles such as dust remaining. Since the convex defect is transparent, it is difficult to observe it in conventional illumination. Thus, we developed an optical system with patterned illumination and an inspection system using imaging technology with a phase-shifting method given the behavior of specular reflection on a gloss surface. The inspected surface is illuminated with the patterned illumination by shifting the phase of a stripe pattern, and a camera takes multiple images of the specular reflection. By calculating the amplitude of the luminance modulation according to a phase-shifting method, the amplitude image can be obtained from the multiple images. The amplitude image means the distribution of the reflectance. The scratch and dirt as well as small convex defects on a gloss surface can be observed in the amplitude image. This inspection system can make an image of the shape and specular reflectance on a gloss surface and allows inspection of gloss coating, which was difficult in the conventional method.