The present invention provides a resin composition for optical shaping that, with its low viscosity, enables easy stereolithographical fabrication of an object, and that can produce an object having desirable toughness and desirable water resistance, particularly for dental mouthpieces and denture base materials. The present invention relates to a resin composition for optical shaping comprising a urethanized (meth)acrylic compound (A) and a photopolymerization initiator (B), the urethanized (meth)acrylic compound (A) being a (meth)acrylate containing at least one polyol moiety and a urethane bond per molecule, said at least one polyol moiety being selected from the group consisting of a polyester, a polycarbonate, a polyurethane, and a polyether each having a structure derived from a C4 to C18 aliphatic chain diol unit (a) having a branched structure.