A pattern inspection apparatus uses a die-to-database comparison method which compares detected pattern data obtained from an optical image of a pattern of a plate to be inspected with first reference pattern data obtained from designed pattern data in combination with a die-to-die comparison method which compares the detected pattern data with second reference pattern data obtained by detecting an area to be a basis for repetition. A computer detects presence of a plurality of repeated pattern areas from layout information contained in the designed pattern data, reads the arrangement, the number, the dimension and the repeated pitch of the repeated pattern areas, and automatically fetches an inspection area of the die-to-die comparison method.