Abstract: A coupling device for mounting a material handling machine, such as a backhoe, on a civil engineering vehicle includes a first bracket assembly secured to the vehicle and a second bracket assembly secured to the machine. The first bracket assembly on the vehicle has a pair of coupling plate members, each of which has upper and lower pin-receiving concave seats that are open upwards. Either of the upper and lower pin-receiving concave seats are formed with locking slots, i.e., throat portions having a reduced width. A pair of upper and lower pins are adapted to be inserted into pin-attaching holes provided in the second bracket assembly secured to the material handling machine. The upper pins having width-reducing portions of a width slightly smaller than the width of the locking slots or throat portions continuous with either of the upper and lower pin-receiving concave seats.