In order to change a size of an imaging area of a tomographic image of an object to be inspected easily  provided is an optical tomographic apparatus for acquiring a tomographic image of an object to be inspected  the optical tomographic apparatus including a control unit for controlling a measuring light path length changing unit to change an optical path length of measuring light in a case where the size of the imaging area of the tomographic image is changed  and for controlling a movable unit for moving a focus lens for focusing the measuring light to the object to be inspected along an optical path to move the focus lens in association with the change in the optical path length of the measuring light