A composition for a support material according to the present invention is to be used in a support material for supporting a model material used to form a shaped article through ink-jet stereolithography and contains polyalkylene glycol having an oxybutylene group, a water-soluble monofunctional ethylenic unsaturated monomer, and a photopolymerization initiator, and the content of the polyalkylene glycol having an oxybutylene group is 15 parts by mass or more and 75 parts by mass or less with respect to the total mass of the composition for a support material taken as 100 parts by mass.