Alignment apparatus

An alignment apparatus for aligning a wafer that is a circular substrate mounted on a mounting unit in a predetermined orientation by optically detecting an alignment mark formed at a backside of the wafer by rotating the mounting unit, the apparatus comprising:

• an imaging unit configured to image, from a position below the wafer, an imaging region having a strip shape extending in a diametrical direction of the wafer across a circumferential edge of the wafer;
• an irradiation unit configured to irradiate light from a position below the wafer toward the imaging region;
• a reflection part configured to reflect toward the imaging region the light that is irradiated from the irradiation unit upwardly while passing through an outside of the wafer, the reflection part having a reflectance making a luminance difference between the outside of the wafer corresponding to the reflection part and the circumferential edge of the wafer in a luminance distribution pattern, obtained by imaging the imaging region, in the diametrical direction of the wafer;
• and
• a control unit configured to detect the alignment mark and the circumferential edge of the wafer based on the luminance distribution pattern.