A difference detecting apparatus include: an image receiving unit that receives at least one or more first images and at least one or more second images; and an exception region acquiring unit that acquires (i) first exception regions that include non-background-color pixels of a first common image, (ii) second exception regions that include non-background-color pixels of a second common image, or (iii) both of the first exception regions and the second exception regions. The difference detecting apparatus includes a first difference detecting unit that detects differences between a first image of attention which is at least one of the first images and a second image of attention which is one of the second images corresponding to the first image of attention except for the first exception regions, the second exception regions, or a union or product of sets of the first exception regions and the second exception regions.