The invention provides a binding device and belongs to the technical field of transportation. The technical problem that an existing binding device cannot easily obtain appropriate binding force on the condition that external force meets standards is solved. The binding device comprises a support and a main binding part. The support is provided with a ratchet wheel tightening mechanism and an auxiliary binding part. A tightening labor-saving assembly is arranged between the support and the auxiliary binding part and comprises a connecting sleeve, a spring and a rotating rod. One end of the connecting sleeve is connected with the support. The rotating rod is arranged in the connecting sleeve. The outer end of the rotating rod extends out of the other end of the connecting sleeve and is connected with the auxiliary binding part. The rotating rod is provided with a thread section. The thread section is in threaded connection with a sliding part. A limiting structure enabling the sliding part to only slide along the rotating rod relative to the connecting sleeve is arranged between the sliding part and the connecting sleeve. The rotating rod is sleeved with the spring. One end of the spring abuts against the sliding part, and the other end of the spring abuts against the connecting sleeve. The binding device has the advantage that acting force will not exceed a specified value when needed binding force is obtained.