A connecting device, comprising: a connecting member, a slider and a locking member, wherein the locking member comprises a limiting cylinder and a limiting button, the limiting button comprises a sliding portion and a transmission portion, and the limiting cylinder is provided with a receiving hole for receiving the transmission portion; wherein one end of the connecting member is provided with a fastening portion to be fitted with an external supporting device, and the other end of the connecting member is provided with a first sliding slot and a limiting slot for accommodating the limiting cylinder; wherein one end of the slider is provided with a second sliding slot slidably fitted with the first sliding slot and an accommodating hole for accommodating the limiting cylinder, a side wall of the slider is provided with a through hole which communicates with the accommodating hole and is configured to receive the transmission portion, and the through hole guides a sliding of the received transmission portion; wherein the other end of the slider is provided with a locking portion for fixing an external device; wherein the first sliding slot of the connecting member is a guide sliding slot formed by a first protrusion portion and a second protrusion portion which are disposed opposite to each other at the other end of the connecting member; and wherein the second sliding slot of the slider is a sliding protrusion which fits with the guide sliding slot; characterized in that the connecting device further comprises: a clamping block; and a clamping bolt, wherein a side wall of the connecting member is provided with a receiving recess which communicates with the first protrusion portion and is configured to receive the clamping block, and a bolt hole is provided at a bottom of the receiving recess; wherein the clamping block is provided with a through hole which corresponds to the bolt hole, and the clamping bolt is configured to pass through the through hole and to fit with the bolt hole; and wherein one end of the clamping block comprises an abutting protrusion that is configured to abut against the sliding protrusion of the slider. a connecting member, a slider and a locking member, wherein the locking member comprises a limiting cylinder and a limiting button, the limiting button comprises a sliding portion and a transmission portion, and the limiting cylinder is provided with a receiving hole for receiving the transmission portion; wherein one end of the connecting member is provided with a fastening portion to be fitted with an external supporting device, and the other end of the connecting member is provided with a first sliding slot and a limiting slot for accommodating the limiting cylinder; wherein one end of the slider is provided with a second sliding slot slidably fitted with the first sliding slot and an accommodating hole for accommodating the limiting cylinder, a side wall of the slider is provided with a through hole which communicates with the accommodating hole and is configured to receive the transmission portion, and the through hole guides a sliding of the received transmission portion; wherein the other end of the slider is provided with a locking portion for fixing an external device; wherein the first sliding slot of the connecting member is a guide sliding slot formed by a first protrusion portion and a second protrusion portion which are disposed opposite to each other at the other end of the connecting member; and wherein the second sliding slot of the slider is a sliding protrusion which fits with the guide sliding slot; characterized in that the connecting device further comprises: a clamping block; and a clamping bolt, wherein a side wall of the connecting member is provided with a receiving recess which communicates with the first protrusion portion and is configured to receive the clamping block, and a bolt hole is provided at a bottom of the receiving recess; wherein the clamping block is provided with a through hole which corresponds to the bolt hole, and the clamping bolt is configured to pass through the through hole and to fit with the bolt hole; and wherein one end of the clamping block comprises an abutting protrusion that is configured to abut against the sliding protrusion of the slider. a clamping block; and a clamping bolt, wherein a side wall of the connecting member is provided with a receiving recess which communicates with the first protrusion portion and is configured to receive the clamping block, and a bolt hole is provided at a bottom of the receiving recess; wherein the clamping block is provided with a through hole which corresponds to the bolt hole, and the clamping bolt is configured to pass through the through hole and to fit with the bolt hole; and wherein one end of the clamping block comprises an abutting protrusion that is configured to abut against the sliding protrusion of the slider.