The present invention provides a detection apparatus for detecting a position of a detection target, including an illumination optical system configured to perform dark-field illumination on a reference mark, and a detection optical system including a sensor configured to detect light from the reference mark and an optical system configured to guide the light from the reference mark to the sensor, and configured to detect a position of the reference mark in a first direction, wherein the reference mark includes one mark element in the first direction, and a width of the mark element in the first direction is set such that two edges of the mark element in the first direction are detected as one peak when the sensor detects the light from the reference mark.