The stereo endoscope apparatus includes: a treatment instrument that is operable； multiple imaging units for imaging a subject, the multiple imaging units acquiring, in response to an operation of the treatment instrument, an image in which the treatment instrument does not appear and an image in which the treatment instrument appears； a detecting section for detecting the area of the image where the treatment instrument appears； an area determining section for determining a replacement area in which an image is to be replaced, the replacement area being at least a part of the area in which the treatment instrument appears； and an image processing section for replacing the replacement area by the image in which the treatment instrument does not appear.
