To provide a coupling device for a towing tractor to be suitable for various draw bar coupling structures on the truck to be drawn side and have a draw bar pin slip-off preventing function, more simplify structure compared with a conventional link mechanism, and be manufactured at a low cost.

A coupling device 1 for a towing tractor comprises a towing bracket 2 disposed at a car body; and a draw bar pin 3. The towing bracket 2 consists of a pair of upper plate 22 and a lower plate 23 in which a coupling hole for inserting the draw bar pin is formed. A drop preventing member 4 having a body part 41 and a protrusion piece 42 protruding therefrom is disposed on the upper part side of the draw bar pin 3. A jumping preventing member 5 in which an insertion hole 51 having diameter larger than that of the body part 41 and a notch part 52 through which a protrusion piece 42 is inserted are formed is disposed on the upper part of the upper plate 22.