A carriage for pipe machining , comprising: a traveling unit equipped with a machining tool for machining a pipe (P), wherein the traveling unit is configured to travel along an outer circumferential surface of the pipe (P); and a roller chain coupled to the traveling unit to wrap around the outer circumferential surface of the pipe (P), wherein the roller chain is configured to guide the traveling unit to travel along the outer circumferential surface of the pipe (P), and is further configured to cause both ends of the roller chain to be coupled to the traveling unit; wherein the roller chain comprises a plurality of unit roller chains which are coupled to each other in succession so as to extend in a longitudinal direction of the roller chain ; and a roller mounted in each of the unit roller chains so that the movement of the roller chain causes the roller of each unit roller chains to rotate on the outer circumferential surface of the pipe (P); wherein the traveling unit comprises: a body ; and a front wheel and a rear wheel that are mounted to a lower portion of the body to roll while in contact with the outer circumferential surface of the pipe (P), characterized in that the front wheel and the rear wheel are movably mounted to a lower portion of the travelling unit , such that a distance between the front wheel and the rear wheel of the traveling unit is adjusted according to a diameter of the pipe (P), and in that the travelling unit further comprises a hook mounted on one side of the body to be coupled to one end of the roller chain . a traveling unit equipped with a machining tool for machining a pipe (P), wherein the traveling unit is configured to travel along an outer circumferential surface of the pipe (P); and a roller chain coupled to the traveling unit to wrap around the outer circumferential surface of the pipe (P), wherein the roller chain is configured to guide the traveling unit to travel along the outer circumferential surface of the pipe (P), and is further configured to cause both ends of the roller chain to be coupled to the traveling unit; wherein the roller chain comprises a plurality of unit roller chains which are coupled to each other in succession so as to extend in a longitudinal direction of the roller chain ; and a roller mounted in each of the unit roller chains so that the movement of the roller chain causes the roller of each unit roller chains to rotate on the outer circumferential surface of the pipe (P); wherein the roller chain comprises a plurality of unit roller chains which are coupled to each other in succession so as to extend in a longitudinal direction of the roller chain ; and a roller mounted in each of the unit roller chains so that the movement of the roller chain causes the roller of each unit roller chains to rotate on the outer circumferential surface of the pipe (P); wherein the traveling unit comprises: a body ; and a front wheel and a rear wheel that are mounted to a lower portion of the body to roll while in contact with the outer circumferential surface of the pipe (P), a body ; and a front wheel and a rear wheel that are mounted to a lower portion of the body to roll while in contact with the outer circumferential surface of the pipe (P), characterized in that the front wheel and the rear wheel are movably mounted to a lower portion of the travelling unit , such that a distance between the front wheel and the rear wheel of the traveling unit is adjusted according to a diameter of the pipe (P), and in that the travelling unit further comprises a hook mounted on one side of the body to be coupled to one end of the roller chain . <EOS>