A hydrous water absorbent polymer-dispersed ultraviolet curable resin composition, a porous substance, an insulated wire, a multilayer covered cable, a coaxial cable using the same, a method for manufacturing the porous substance and a method for manufacturing the insulated wire using the same. A hydrous water absorbent polymer preliminarily hydrated and swollen is dispersed in an ultraviolet curable resin composition. The ultraviolet curable resin composition includes an urethane oligomer having a molecular weight of 5000 or less and having a poly(ethylene-glicol-adipate)diol having a molecular weight of 500 to 3000 and having an acryloyl radical or a methacryloyl radical as a functional radical X at both ends by urethane bond via an alicyclic isocyanate as expressed by a following formula, at least one kind of alicyclic monomer, a hydrophilic monomer, and a photopolymerization initiator. 0.01 mass % to 0.5 mass % of a non-ionic fluorine based surface active agent or a non-ionic silicone-based surface active agent may be added to the resin composition.