An image processing of an object to be detected in bonding system for manufacturing, for instance, semiconductor devices including a step of calculation of a difference value between a reference image inputted beforehand and a rotated image obtained by rotating the reference image for a plurality of reference points within the reference image, a step of mask pattern production based upon the difference values for the plurality of reference points, and a step of position detection for a position of an object of detection by pattern matching by way of using an image of the object of detection obtained by imaging the object of detection, the reference image and the mask pattern.