An occupant restraining device for a vehicle has: a time to collision estimating section that estimates a time to collision, the time to collision being a time until a front collision with a vehicle ahead; a force imparting portion that imparts force toward a vehicle rear side to a vehicle occupant of an own vehicle; a gap enlarging portion that enlarges a gap between the vehicle occupant and a seatback of a vehicle seat; a gap estimating section that estimates a size of the gap between the vehicle occupant and the seatback; and a control section that, in a case in which the gap enlarging portion operates, controls a timing of a start of operation of the force imparting portion on the basis of the time to collision estimated by the time to collision estimating section and the size of the gap estimated by the gap estimating section.