The invention discloses a device for automatically polishing the outer surfaces of steel pipes. The device comprises a frame body, a plurality of placing roller set mechanisms, a plurality of polishing set mechanisms and a control cabinet, wherein the plurality of placing roller set mechanisms are arranged on the frame body at intervals and used for placing the steel pipes to be polished; the plurality of polishing set mechanisms are arranged on the frame body at intervals, the polishing set mechanisms and the placing roller set mechanisms are arranged at intervals, and the polishing set mechanisms are used for polishing the outer surfaces of the steel pipes; and the control cabinet is arranged outside the frame body, and the placing roller set mechanisms and the polishing set mechanisms are all electrically connected with the control cabinet. According to the device, the steel pipes are placed on the placing roller set mechanisms, then the control cabinet controls placing rollers to rotate to drive the steel pipes to rotate, and the outer surfaces of the steel pipes are automatically polished by the polishing set mechanisms, so that the labor intensity is reduced, and the polishing efficiency is improved; and the device is simple and practical in structure, high in efficiency, and capable of meeting machining requirements, saving manpower and material resources, reducing machining cost, and effectively removing pits and corrosion spots on the outer surfaces of the steel pipes.