Abstract: For checking the workmanship of paint coating, light is shed on the portion of the surface of an object where a paint has been applied. The intensity of light reflected by this portion of the surface gives a clue to a judgment on the acceptability of the paint coating. The judgment is passed by checking whether or not the above-mentioned intensity of light falls within a preset level. The level to be preset is variable according to the intensity of light reflected by the surface, the intensity of light in this case being measured prior to the application of the paint. The light reflected by the portion of the surface where the paint has been applied is resolved into three colors. A checkup is carried out on whether or not the sum of the intensities of light representing these three colors corresponds to a level preset for the amount of this sum. A level to be preset is selected from among data stored in a memory.