A method for acquiring an optical tomographic image is disclosed. The method acquires the optical tomographic image based on a result of a Fourier transform of an interference light spectrum obtained by dividing light into first branched light and second branched light and causing mutual interference between reflected light and diffused reflected light. The reflected light arises at a reflecting body when the first branched light is irradiated onto the reflecting body. The diffused reflected light arises when the second branched light is irradiated onto an examination region. The acquisition method includes: acquiring a first optical tomographic image when an examination object is arranged in the examination region acquiring a second optical tomographic image when the examination object is not arranged in the examination region and acquiring the optical tomographic image based on a difference between the first optical tomographic image and the second optical tomographic image.
