The invention relates to a device for a coupling an agricultural implement to an agricultural tractor, in which the operation to release the coupling between the agricultural implement and the agricultural tractor can be easily implemented.When the coupling of the agricultural tractor and the agricultural implement is released, first, a control lever of a coupling hook is slid upward against the urging force of a spring until a second guide pin reaches the lower end of a slit. Next, the control lever is turned forward around the second guide pin until a bent portion of the upper portion and the lower portion of the control lever comes into contact with a first guide pin. As a result, the rear end of a stopper is retracted into a cavity in the hook main body of the device through a second opening so as to slide to the coupling-ball-releasing position, and a groove of the stopper is hooked to a hooking pin so as to be fixed.