The invention discloses a derusting device for an outer surface of a pipeline. The derusting device comprises a workbench and a base, wherein a plurality of damping devices are arranged between the workbench and the base; struts are arranged on the upper side of the workbench; a mounting plate is arranged at the upper ends of the struts; first motors are arranged on the upper side of the mounting plate in left-right symmetry; first threaded rods are arranged at the output ends of the first motors; the first threaded rods are in threaded connection with a supporting plate; mounting bases are arranged on the lower side of the supporting plate in left-right symmetry; a second threaded rod is arranged between the two mounting bases; a second motor which drives the second threaded rod is mounted at the right end of the lower side of the supporting plate; the second threaded rod is in threaded connection with a sliding block; a fixed table is arranged at the left part of the upper side of the workbench; a fixed block is arranged on the right side of the fixed table; a slide rail is arranged at the right part of the upper side of the workbench; a sliding table is arranged on the slide rail; and another fixed block is arranged on the left side of the sliding table. According to the derusting device, structure is simple, utilization is convenient, utilization cost is reduced, the damping effect is good, and dust pollution is reduced.