The substrate detection apparatus includes: a collimating reflector located on one side of substrates; an illumination unit configured to radiate light in a planar state toward the collimating reflector such that edge portions of the substrates are located in an optical path of the light; an image acquiring unit configured to acquire a passing light image including the edge portions formed on the collimating reflector with the light radiated in the planar state from the illumination unit; and an image processing unit configured to process the passing light image obtained by the image acquiring unit, thereby detecting the conditions of the substrates.