1. An imaging device, comprising: an imaging unit having first pixels configured to photoelectrically convert, with use of a photoelectric conversion element group, a subject image which is imaged with a photographic lens and to output a first image signal, and second pixels configured to be placed discretely between the first pixels so as to photoelectrically convert, with use of the photoelectric conversion element group, each of a plurality of subject images which come from divided pupil regions formed by dividing a pupil region of the photographic lens and to output second image signals having a phase difference; an imaging control unit configured to control the imaging unit so as to simultaneously image the first image signals and the second image signals; a parallax information calculation unit configured to calculate parallax information based on the second image signals outputted from the imaging unit; a plane image generation unit configured to generate a plane image based on the first image signals outputted from the imaging section; and a blurring processing unit configured to determine target pixels in the plane image which are to be subjected to blurring processing, based on the parallax information calculated by the parallax information calculation unit, and to perform blurring processing on the determined target pixels in the plane image.