The invention discloses an automatic shot blasting machine for the inner and outer walls of a large-diameter steel pipe. The automatic shot blasting machine comprises a frame, a steel pipe rotating system, a shot blasting mechanism, a shot circulating system and a dedusting system, wherein the steel pipe rotating system is adaptable to rotating of a plurality of large-diameter steel pipes through adjustment and is especially applicable to large-diameter steel pipes; the shot blasting mechanism is provided with altogether six shot blasting devices, with three shot blasting devices acting on the outer walls of the steel pipe while the other three acting on the inner walls of the steel pipe; the shot circulating system is used for cyclic utilization of steel shots; and the dedusting system is used for removing dust in the steel shots. Compared with traditional rust removal technology, the automatic shot blasting machine provided by the invention has the advantages of lower power consumption, smaller work amount, reduced usage cost and higher efficiency; the automatic shot blasting machine does not raise a great amount of dust, changes the working environment of workers and is benefit for health of the workers; and the automatic shot blasting machine has a wider application scope and is especially applicable to rust removal of large-diameter steel pipes.