The present invention provides a detection apparatus which detects an original mark on an original and a substrate mark on a substrate, the original mark and the substrate mark being arranged via a projection optical system, the apparatus comprising an optical system including an imaging device and configured to form an image of the original mark and an image of the substrate mark onto the imaging device, wherein the optical system includes a detection reference member having a first mark and a second mark, and is configured to form an image of the first mark onto the original, form an image of the second mark onto the substrate via the projection optical system and the original, and form the image of the first mark, and the image of the second mark onto the imaging device.