An imaging apparatus includes: an image sensor capturing an image of a subject via an optical system including a focus lens, and generating image data; a distance measuring part calculating a subject distance and a movement distance of the subject by using the generated image data; and a controller that performs an auto-focus action by using the calculated subject distance or movement distance. The distance measuring part uses: first image data when the subject lies at the first position; second image data when the subject lies at the second position; and a PSF of the optical system corresponding to a focused position of the subject lying at the first position, thereby finding a distance between the first position and the second position, and calculating the subject distance and the movement distance of the subject for an image indicated by the second image data based on the found distance.