To provide an inexpensive document size detection apparatus capable of precisely detecting a document size by a simple constitution.

The document size detection apparatus comprises: a moving terminal 5 which is affixed to a movable guide 3 regulating the end position of the document not shown in the figure and moves with the movable guide 3; a fixation terminal unit 7 on which a plurality of fixation terminals 6 with which the moving terminal 5 is in contact are formed at predetermined intervals; and a detection unit 9 which comprises detection circuits 8 which are provided on the basis of being one-to-one with the fixation terminals 6 and output a detection signal when the moving terminal 5 comes into contact with a fixation terminal 6.