In a hydraulic composition for additive manufacturing which includes (A) at least one water-soluble hydroxyalkyl alkyl cellulose selected from hydroxypropyl methyl cellulose and hydroxyethyl methyl cellulose, (B) a defoamer, (C) cement, (D) water, (E) polyvinyl alcohol and (F) borax, the water-soluble hydroxyalkyl alkyl cellulose has an alkoxy group degree of substitution of from 1.6 to 2.0 and a 2 wt% aqueous-solution viscosity at 20°C of from 50 to 1,000 mPa·s, the polyvinyl alcohol has a degree of saponification of from 70 to 90 mol% and a 4 wt% aqueous-solution viscosity at 20°C of from 20 to 80 mPa·s, and the water is added in an amount of from 25 to 70 parts by weight per 100 parts by weight of the cement. The composition has a good extrudability from a nozzle and a good self-supportability following deposition.