The invention relates to the technical field of ion beams, in particular to a polishing device and method utilizing in-situ sputtering combined with ion beam etching. The polishing device comprises atransfer chamber, an etching chamber, a sputtering deposition chamber and gate valves, the gate valves are arranged between the transfer chamber and the etching chamber as well as between the etchingchamber and the sputtering deposition chamber, and workpiece conveying devices for conveying workpieces among the transfer chamber, the etching chamber and the sputtering deposition chamber are arranged in the transfer chamber, the etching chamber and the sputtering deposition chamber. The polishing method applying the polishing device comprises the processes that the workpieces are loaded in thetransfer chamber first, then the workpieces are subjected to ion beam cleaning in the etching chamber, then a layer of thin film layer (sacrificial layer) is deposited on each workpiece in a sputtering mode in the sputtering deposition chamber, then the workpieces are subjected to ion beam correction polishing in the etching chamber, finally, the workpieces are taken out through the transfer chamber, and polishing of optical elements is achieved.