There is disclosed a fire-retardant resin composition, which comprises: a thermoplastic resin component (A) comprising (a) a block copolymer mainly made of a vinyl aromatic compound and a conjugated diene compound as its constitutional components, and/or a hydrogenated block copolymer of the block copolymer, (b) a nonaromatic-series softener for rubber, (c) an ethylene/.alpha.-olefin copolymer, and (d) a polypropylene resin; and (e) an organic peroxide, (f) a (meth)acrylate-series and/or allyl-series crosslinking aid, and a metal hydrate (B), wherein a specific amount of the metal hydrate (B) to be used is a metal hydrate being pretreated with a silane coupling agent, and the fire-retardant resin composition is a mixture of the above formulation that is heated and kneaded at a temperature equal to or higher than the melting temperature of the (A). There is also disclosed a wiring material and other molded parts, in which the resin composition is utilized.