A vehicular opening/closing body control device includes: a braking control unit configured to apply a braking force to an opening/closing body provided in an opening in a vehicle; a traveling state determination unit configured to determine a traveling state of the vehicle; an abnormality detection unit configured to detect occurrence of a full-closing abnormality in which the opening/closing body is not held in a fully-closed state during the traveling of the vehicle; and a record holding unit configured to hold a detection record of the full-closing abnormality, wherein the braking control unit executes braking control through detection of the full-closing abnormality of the opening/closing body, and in a case where the detection record of the full-closing abnormality is held after the vehicle stops, executes the braking control of the opening/closing body based on the detection record of the full-closing abnormality before the vehicle travels.