To improve both forming limit and forming accuracy in friction stir incremental forming, multistage forming was carried out. JIS: A5052-H34 aluminum alloy sheets with a size of 100 mm × 100 mm × 0.5 mm were employed for specimens. The sheets were formed into a frustum of conical shape and forming limit was evaluated by the formable minimum wall angle without fracture. The formable minimum wall angle by single- and two-stage friction stir incremental forming was 70 ° and 72 °, respectively. When the wall angle was set to 70 ° and the sheets were formed by single- and two-stage forming, the formed shape by two-stage forming was closer to the objective shape than that by single-stage forming. The deformation of the sheet was shearing in single-stage forming, but that was two axis stretching in two-stage forming