Provided is a water-soluble composition for optical three-dimensional modeling having little burden on the environment, which enables the production of a three-dimensional model that has both little warping deformation and excellent mechanical characteristics, while exhibiting good adhesion between cured film layers during the production process of the three-dimensional model; and a method for producing a three-dimensional model, which uses this composition for optical three-dimensional modeling. Specifically provided is a water-soluble composition for optical three-dimensional modeling, which contains (A) 10-70% by mass of a water-soluble cationically polymerizable compound that is an ether derivative compound of a sorbitol having a glycidyl ether structure, (B) 1-30% by mass of a water-soluble radically polymerizable compound having a methacryl group and/or an acryl group, (C) 0.1-20% by mass of an antimony-free cationic polymerization initiator that is a sulfonium compound or a bis(alkylphenyl)iodonium compound, and (D) 0.1-20% by mass of a radical polymerization initiator.