There is provided a method for manufacturing a three-dimensional shaped object by alternate repetition of a powder-layer forming and a solidified-layer forming by an irradiation with a light beam in order to provide a selective laser sintering method capable of reducing a warp of the three-dimensional shaped object, the warp being due to a stress around an upper surface of the three-dimensional shaped object. Especially, in the present invention, a part of a region for the formation of the solidified layer is not irradiated with the light beam to form a non-irradiated portion, thereby providing at least one slit-groove at an upper surface of the three-dimensional shaped object, the slit-groove being for reducing a stress of the three-dimensional shaped object.