PURPOSE: To enable parts to be mounted with improved accuracy by providing means for calculating the amount of deviation between the chuck position and the reference position of electronic parts by the chuck means.

CONSTITUTION: A lead A is recognized and the coordinates of image at this time is set to (x1, y1). In a similar manner, the image of lead C is recognized and the coordinates are set to (x4, y4). Also, the coordinates of a chuck nozzle 19 at this time are set to (x9, y9). Using the above coordinates, the distance from the center of the chuck nozzle 19 to the leads A and C retaining an IC10 is calculated. Then, a correction value is given being based on this result to allow the IC10 retained by the chuck nozzle 19 to be mounted onto a circuit substrate 11. It allows mounting accuracy to be improved and various kinds of parts including ultra-small parts to be fitted with required accuracy.