In order easily to change a size of an imaging area of a tomographic image of an object to be inspected, an optical tomographic apparatus is provided for acquiring a tomographic image of an object to be inspected, the optical tomographic apparatus including means (900) for changing the optical path length of a measuring light means (119) for changing the path length of a reference light means for instructing a size of an imaging area for the tomographic image and control means for controlling the measuring light path length changing means (900) and the reference light path length changing means (119) in response to the instruction by the instructing means.
