The invention discloses a guide pipe external circle grinding device, and particularly relates to the technical field of machining. The guide pipe external circle grinding device comprises a machine frame, a belt is connected between an output shaft of a motor and a polishing barrel, the output shaft of the motor is further provided with a cam, a transmission mechanism is arranged on the machine frame and located below the cam, a dust removal mechanism is arranged on the transmission mechanism, polishing bristles are arranged in the polishing barrel, a conveying frame is fixed to the portion,between the polishing barrel and an air cylinder, of the machine frame, an inclined plate is connected between the conveying frame and the bottom of the machine frame, the inclined plate is provided with inclined teeth and further provided with a vibrator, two supporting rods are fixed over the inclined plate, a rotating shaft is rotationally connected between the two supporting rods, polishing plates are arranged on the two sides of the rotating shaft correspondingly and connected between the two supporting rods in a sliding mode, the supporting rods are provided with limiting columns, and apiston rod of the air cylinder is provided with a first push plate. By the adoption of the technical scheme, the problem that an existing guide pipe external circle grinding device is large in labor intensity is solved, and grinding machining for the external circle of an automobile guide pipe can be achieved.