Abstract: In order to improve a trailer device for motor vehicles, comprising a crossmember, which is mountable on a vehicle body at the rear-end side thereof, a holding unit, which is provided on the crossmember and which carries a ball neck receiving body comprising a ball neck receptacle, into which receiving body an insertion portion of a ball neck supporting a coupling ball is insertable and fixable therein, in such a way that the ball neck receiving body is both visible and intrusive to the least possible extent when the ball neck is not inserted, it is proposed that the holding unit comprises a pivot bearing unit, by means of which the ball neck receiving body is movable from a working position, in which the ball neck is insertable into said receiving body for trailer operation, into a rest position, and that at least one stop element fixedly connected to the holding unit is provided, which stop element has a first support surface, which, in the working position, abuts against the insertion portion with the inse