Abstract: The method for manufacturing an additively manufactured object includes: forming a precursor having an opening portion that communicates with an internal space, by jetting a liquid binder onto a powder layer to form solidified layers and stacking the formed solidified layers; forming a plug configured to be assembled with the opening portion; removing unsolidified powder remaining in the internal space from the opening portion; applying the liquid binder to an outer peripheral wall of the plug after removing the unsolidified powder; assembling the plug with the opening portion such that the outer peripheral wall of the plug comes into contact with an inner peripheral wall of the opening portion; and sintering the precursor having the plug assembled with the opening portion.