The invention relates to an elastic fluorohydrocarbon resin. This resin is obtained by graft copolymerization of a first segment which is one of fluorine-containing elastomeric and crystalline polymers with a second segment which is the other of these polymers. The first segment is prepared by copolymerizing at least one first unsaturated monomer that has peroxy bond with at least one second fluorine-containing monomer. When the first monomer is dissolved in a first solvent prior to the copolymerization, the copolymerization can be safely conducted with higher yield. This first solvent is selected from a carboxylic ester of t-butanol, methylene chloride, 1,1,1-trichloroethane, and first, second, third and fourth compounds which are respectively represented by R.sup.1 COOR.sup.2, C.sub.2 H.sub.x Cl.sub.y F.sub.z, C.sub.3 H.sub.x Cl.sub.y F.sub.z, and C.sub.4 H.sub.x Cl.sub.y F.sub.z. When the fluorine-containing elastomeric copolymer as the first segment is purified by contact with a barium salt prior to the graft copolymerization, the elastic fluorohydrocarbon resin becomes improved in thermal stability. When the fluorine-containing elastomeric copolymer having a water content of 0.1-50 wt % as the first segment is dispersed in a liquid medium containing t-butanol and water, it becomes unnecessary to dry this elastomeric copolymer prior to the graft copolymerization. When the fluorine-containing elastomeric copolymer as the first segment is dispersed in another liquid medium containing t-butanol, water, a carboxylic ester and barium hydroxide, the elastic fluorohydrocarbon resin becomes improved in thermal stability with higher graft copolymerization rate.