An optical tomographic image acquisition apparatus comprises a light source unit emitting light; a light dividing device dividing the light from the unit into measurement light and reference light; a projecting device arranged inside a tubular sheath to project the measurement light onto an object; a combining device combining reflected light reflected from the object or the sheath and the reference light; an interference light detecting device detecting interference light between the reflected light and the reference light; an interference signal acquiring device acquiring an interference signal; a tomographic image acquiring device acquiring an optical tomographic image; and a reference position adjustment section detecting a sheath interference signal that is an interference signal of the reflected light reflected from the sheath from the interference signals and adjusts an optical tomographic image reference position as a reference to acquire the optical tomographic image based on the detected sheath interference signal.