A three-dimensional object producing method including: forming a powder material layer with a powder material for three-dimensional object formation, where the powder material includes a base material and a resin including a reactive functional group; and applying a curing liquid to the powder material layer to form a cured product, where the curing liquid contains a curing agent capable of forming a covalent bond with the reactive functional group, wherein the curing agent includes an aliphatic compound having two or more isocyanate groups at a molecular terminal thereof.