Overlap detection apparatus and overlap detection method

An overlap detection apparatus mounted to a printing press includes a sheet detection sensor for detecting whether a portion of the sheets passing a given position is a non-overlapping portion or an overlapping portion; a signal output section for outputting an overlapping signal on the basis of the detected results of the sheet detection sensor, in which the overlapping signal takes a first form for the overlapping portion and takes a second form for the non-overlapping portion; and a determination section for determining that the sheets of paper are being correctly conveyed while each being displaced by a given amount from an upstream sheet of paper in the conveying direction and overlapping the same when a portion of the overlapping signal taking the first form is equal to a given reference portion, and determines that the sheets of paper are not being correctly conveyed when the portion of the overlapping signal taking the first form is not equal to the given reference portion.