A guide mark to avoid obstacles backward contacts the vehicle body side, together with intuitively grasp can perform the guide mark of the alignment of the towing vehicle side coupler and the towing vehicle side coupler, the towing vehicle-side coupling ingredients and driving support apparatus to maintain the visibility state of the tractor-side coupling. This device, the towing vehicle side connector (402) to the vehicle rear of the captured image including a towed vehicle side connector (404), the vehicle expected pair of planar corresponding to the steering trajectory guide mark (405) to the (406) display means a superimposed image obtained by superimposing (103). Image superimposition unit (112) is predicted locus guide mark (405), (406) the vehicle width center side of the side of the (405a), superimposed on the outer direction from (406a) to the towing vehicle side connector (402) , predicted locus guide mark (405), (406) the vehicle width direction outer edge of the sides of the (405 b), superimposes the (406b) as a predicted locus of the vehicle-side end.