An exposure method for projecting a pattern formed on a reflection plate onto a substrate, via a projection optical system, using extreme ultraviolet light. The method includes a detection step of detecting a relative position between a second mark formed on a plate holding unit for holding the reflection plate and a third mark formed on the reflection plate. The detection step includes sub-steps of (i) detecting light reflected from the second mark with a detector, (ii) detecting light reflected from the third mark with the detector, and (iii) changing a relative position between the plate holding unit and the detector between sub-steps (i) and (ii).