PURPOSE: To surely and simply constitute a connecting apparatus of working machine connected through a three-point link mechanism to the rear of a tractor.

CONSTITUTION: In a connecting apparatus B of working machine C laterally arranging a connecting plate 4a providing an engaging recessed part 10a engaging with a top pin 6 of a working machine C in the upper part of a hitch frame 4 and providing an engaging recessed part 4c engaging with lateral lower pins 5 of the working machine C in the lower part of the hitch frame 4 and rotatably providing a hook 7 for lock on the connecting plate 4a, a spring for engaging and pressing the hook 7 for lock with the lower pin 5 and a member which works as a stopper in releasing lock or waiting connection are integrally formed and provided and a roll off 8a is provided in the member which works as the stopper in releasing lock or waiting connection.