Provided is a composition for optical stereolithography the stereolithography (photocuring) of which is completed in a shorter time and which provides a stereolithographic object having excellent strength (strength that prevents the occurrence of a fracture and the like when the stereolithographic object is subjected to an impact, or dropping, and strength with which the stereolithographic object can withstand repeated folding). The composition for optical stereolithography of the present invention includes (A) a diallyl phthalate-based polymer; (B) radical polymerizable compounds having a methacrylic group and/or an acrylic group; (C) a radical polymerization initiator; and (D) a sensitizer. The (B) radical polymerizable compounds includes at least (B1) an epoxy (meth)acrylate having a methacrylic group and/or an acrylic group, or (B2) a dioxane (meth)acrylate having a methacrylic group and/or an acrylic group. The composition contains 0.5 to 10% by mass of (A), 5 to 43% by mass of (B1) and (B2), 20 to 95% by mass of (B) other than (B1) and (B2), 0.1 to 5% by mass of (C), and 0.1 to 5% by mass of (D).