This invention relates to: a molding material comprising a bundle of continuous reinforcing fibers (A), a polyarylene sulfide prepolymer (B) comprising at least 50% by weight of cyclic polyarylene sulfide and having the weight average molecular weight of less than 10,000 or polyarylene sulfide (B′) having the weight average molecular weight of 10,000 or greater and the degree of dispersion of 2.5 or lower, and thermoplastic resin (C); a prepreg comprising a resin composition comprising the polyarylene sulfide prepolymer (B) impregnated into a reinforcing fiber; and a method for producing a fiber-reinforced molding substrate comprising step (I) of continuously feeding a bundle of continuous reinforcing fibers, step (II) of combining cyclic polyarylene sulfide with the reinforcing fiber bundle, step (III) of heating the composite obtained in step (II) to subject the cyclic polyarylene sulfide to ring-opening polymerization to convert into polyarylene sulfide, and step (IV) of cooling the composite obtained in step (III) and withdrawing the same.