PURPOSE: To apply very correct holing to a printed board by calculating the average value of errors after multiple error measurements, correcting the relative position between the printed board and a holing means based on it, then holing the printed board.

CONSTITUTION: The marks of measuring boards are image-recognized, holing is applied based on it, errors between mark positions and holed positions are obtained for respective error measuring boards, and the average value of them is calculated. The positioning mark of a printed board to be actually holed is image-recognized, the correction based on the error average value is applied to the image recognition result, a holing means is moved to the corrected holing position, then the printed board is holed.