A driving support apparatus comprising: an image acquiring section that acquires a captured image of an area behind a vehicle supported by the apparatus, the area including a tow coupler at a rear portion of the vehicle and a tow-target coupler of a tow-target vehicle to be coupled to the tow coupler; and a superimposing section that superimposes a pair of left and right planar predicted-trajectory guide marks (405, 406) in accordance with steering operation of the vehicle supported by the apparatus, on the captured image acquired by the image acquiring section and that outputs the superimposed image, the left planar predicted-trajectory guide mark includes at least a first line that forms a first side of the left predicted-trajectory guide mark located on a center side of a vehicle width direction and a second line that forms a second side of the left predicted-trajectory guide mark located on an outer edge side of the vehicle width direction, the first line being separated from the second line; the right planar predicted-trajectory guide mark includes at least a third line that forms a third side of the right predicted-trajectory guide mark located on the center side of the vehicle width direction and a fourth line that forms a fourth side of the right predicted-trajectory guide mark located on the outer edge side of the vehicle width direction, the third line being separated from the fourth line; the superimposing section superimposes the first and third lines (405a, 406a) of the left and right predicted-trajectory guide marks (405, 406) respectively at positions in an outer edge direction from the tow coupler, the first and third lines (405a, 406a) being located on the center side of the vehicle width direction; and the superimposing section superimposes the second and fourth lines (405b, 406b) of the left and right predicted-trajectory guide marks (405, 406) respectively as predicted-trajectories of both lateral edges of the vehicle supported by the apparatus, the second and fourth lines (405b, 406b) being located on the outer edge side of the vehicle width direction, characterized in that the superimposing section changes an image to be superimposed between a tow guide and a normal backward assistance other than the tow guide, and in the case of the normal backward assistance, the superimposing section does not superimpose the first and third lines (405a, 406a) of the left and right predicted-trajectory guide marks (405, 406) respectively at the positions in the outer edge direction from the tow coupler. an image acquiring section that acquires a captured image of an area behind a vehicle supported by the apparatus, the area including a tow coupler at a rear portion of the vehicle and a tow-target coupler of a tow-target vehicle to be coupled to the tow coupler; and a superimposing section that superimposes a pair of left and right planar predicted-trajectory guide marks (405, 406) in accordance with steering operation of the vehicle supported by the apparatus, on the captured image acquired by the image acquiring section and that outputs the superimposed image, the left planar predicted-trajectory guide mark includes at least a first line that forms a first side of the left predicted-trajectory guide mark located on a center side of a vehicle width direction and a second line that forms a second side of the left predicted-trajectory guide mark located on an outer edge side of the vehicle width direction, the first line being separated from the second line; the right planar predicted-trajectory guide mark includes at least a third line that forms a third side of the right predicted-trajectory guide mark located on the center side of the vehicle width direction and a fourth line that forms a fourth side of the right predicted-trajectory guide mark located on the outer edge side of the vehicle width direction, the third line being separated from the fourth line; the superimposing section superimposes the first and third lines (405a, 406a) of the left and right predicted-trajectory guide marks (405, 406) respectively at positions in an outer edge direction from the tow coupler, the first and third lines (405a, 406a) being located on the center side of the vehicle width direction; and the superimposing section superimposes the second and fourth lines (405b, 406b) of the left and right predicted-trajectory guide marks (405, 406) respectively as predicted-trajectories of both lateral edges of the vehicle supported by the apparatus, the second and fourth lines (405b, 406b) being located on the outer edge side of the vehicle width direction, characterized in that the superimposing section changes an image to be superimposed between a tow guide and a normal backward assistance other than the tow guide, and in the case of the normal backward assistance, the superimposing section does not superimpose the first and third lines (405a, 406a) of the left and right predicted-trajectory guide marks (405, 406) respectively at the positions in the outer edge direction from the tow coupler.