In recent years, automation inspection systems using image processing are developed in appearance inspection of production lines of the factories. In this research, a sealant inspection system was built. This sealant is used in order to prevent water leakage coming from outside of a car. The sealant inspection system inspects whether the sealant is applied appropriately. When inspecting, specular reflection occurs on the sealant surface in response to the influence of various ambient light. Thus, there is a problem. The system is not able to extract the sealant region correctly. Therefore, we propose the extraction method of sealant region using color pattern illumination and YCbCr color space characteristics.