A processing device which obtains distance information of a subject, including: a calculation unit configured to calculate the distance information of the subject from a difference in blur degree of a plurality of images photographed by an imaging optical system; a correcting unit configured to correct the distance information using correction data in accordance with an image height in the imaging optical system; and an extraction unit configured to extract at least one frequency component from each of the plurality of images, wherein the calculation unit calculates the distance information from a difference in blur degree in the plurality of images in the at least one frequency component; and the correcting unit corrects the distance information using correction data in accordance with an image height in the at least one frequency component.