The possibility of the incremental flattening of the bends of 5052 aluminum alloy sheets was experimentally examined by computerized numerical control (CNC) incremental hammering. The experimental results indicated that flattening was possible and that the metal flow behavior depended on the rotational direction of the tool and the hammering pitch. It was also clarified that the transcription accuracy of the envelope surface of the tool was improved by four-pass incremental flattening and that the thickness of the flattened part was greater than that of the mother sheet.