Abstract: Disclosed is an automatic welding apparatus using an inside steel tube, which includes a connecting seat and a fixing bracket. The fixing bracket is fixedly connected to a rear side of the connecting seat. a roller assembly is provided at one end of the fixing bracket, and a left side and a right side of the connecting seat are respectively fixedly connected with two first mounting brackets, between which a connecting shaft is rotatably connected. The connecting shaft is rotatably connected with a driving wheel, a signal transmission component is arranged on a periphery of the driving wheel, a laser welder is provided on an upper surface of the connecting seat, a laser welding head is provided at one end of the laser welder; and the laser welder is configured to start the laser welding head according to a signal transmitted by the signal transmission component.