The imaging device of the present invention includes: an image sensor 14 that is configured such that a plurality of pixels having an organic layer (14-4) for photoelectric conversion is two-dimensionally arranged, and each pixel of the image sensor (14) is divided into a plurality of regions, and has an on-chip microlens (15), which forms a pupil image of a optical imaging system on the plurality of regions, and reading sections (16) which respectively read photoelectrically converted signals of the plurality of divided regions; an optical diaphragm that mechanically stops down rays which are incident into the image sensor 14; and an electronic diaphragm section that electronically controls an aperture value, and that selects signals of the divided regions corresponding to the aperture value from the signals of the plurality of divided regions, on the basis of the aperture value which is controlled by the optical diaphragm.