An imaging device of the present disclosure includes: an optical system including a focus lens; an imaging system configured to generate image data based on an image obtained by the optical system; a DFD processing unit configured to calculate DFD distance information regarding a subject distance based on a plurality of blur signals and a plurality of pieces of image data having different focusing positions, the image data being obtained from the imaging system following drive of the focus lens; a measuring unit configured to measure a variation of a subject image of the image data; and a control unit configured to control the DFD processing unit to calculate the DFD distance information when the variation is equal to or more than a predetermined value.