To classify causing processes and kinds of defects rapidly, accurately and automatically, in a defect classification of a color display screen.

The defect classification method of the color display screen which has a color display pixel region made up like a matrix by a pattern formed on a transparent substrate, uses a vertical illumination image and a transmitted illumination image, and by using at least one of above images, executes a step in which a pattern matching process is carried out between an image with a defective pixel and an adjacent image with a defect-free pixel having a display color identical to that of the defective pixel, a step in which a defect candidate is extracted from a difference image generated by the pattern matching process between the images with the defective and defect-free pixels, a step in which the position of the defect candidate is determined, and a step in which the defect candidate is discriminated by its appearance.