An imaging device includes a capturing lens; an imaging element in which a pair of horizontal light receiving units receiving a pair of split light of a horizontal direction and a pair of vertical light receiving units receiving a pair of split light of a vertical direction are two-dimensionally arranged; a movement unit that moves the imaging lens in the optical axis direction; a specifying unit that specifies one of the pair horizontal light receiving units or the pair vertical light receiving units, of which the calculated absolute value of the signal amount difference is smaller; and a control unit that performs correlation computation based on the signal amount of the plural photoelectric conversion elements aligned in a direction of the specified one of the pair of horizontal light receiving units or the pair of vertical light receiving units and controls the movement unit based on the correlation computation.