A carrier and a substrate are aligned even if an imager cannot be simultaneously focused on alignment marks formed on both the carrier and the substrate. Center of gravity positions G1m of an alignment pattern element AP1 on a substrate and G2m of an alignment pattern element AP2 on a transparent blanket are calculated by image processing from an image IM imaged via the blanket by a CCD camera. The position of the center of gravity Gm2 is specified by a process associated with edge extraction from the image imaged with the alignment pattern element AP2 on the blanket being in focus. High spatial frequency components are removed and low frequency components are extracted for the alignment pattern element AP1 on the substrate imaged out of focus to have a blurred outline, and the position of the center of gravity G1m is specified from an extraction result.