To provide a retreat auxiliary device for a connected vehicle for automatically correcting a curve and improving linearity when the connected vehicle is retreated.

When a difference in the number of revolutions of left and right wheels 3, 4 is generated when a trailer 2 is retreated by a controller 7 inputting signals of wheel speed sensors 5, 6 detecting number of revolution of left and right wheels 3, 4 of the trailer 2, the side of the wheel having a larger number of revolutions is braked so as to eliminate the difference in the number of revolutions of both of left and right wheels 3, 4 by the controller 7 and moving distances of the left and right wheels 3, 4 are made equal.