PURPOSE: To easily detect the position of an alignment mark by using dispersed light or diffracted light generated in the interface between the 1st and 2nd transparent parts to detect the mounting position.

CONSTITUTION: A pattern width (t) of an alignment mark 1 is selected to have a sufficiently small value compared to the resolution of a detection microscope for detecting the position of the alignment mark 1 and the alignment mark 1 is formed to have the shape of a cross as a whole so that the dislocation in the X and Y directions may be detected by one alignment mark (L). When the alignment mark is detected by the detecting microscope, the position of the alignment mark is detected by the same method as that in the case where a light spot (SP) is equivalently scanned. And by detecting the position of the alignment mark using dispersed light and diffracted light generated in the interface between the transparent members, the position of the alignment mark is easily detected even when the alignment mark is formed out of the transparent member like when it is formed out of an opaque member.