Electrical conducting Poly(ethylene terephthalate)(PET)film was obtained by introducing Cu2-xS(0 x 0.2), which is known as p-type semiconductor, in the electrically insulating PET film. The cyano group was introduced into the PET film in order to accept Cu2-xS seim-conductor. Acrylonitrile having cyano group was utilized to carry out grafting on PET film using benzoyl peroxide as the initiator. Extent of grafting depended upon the reaction time, concentration of initiator, and the monomer as well as on the reaction temperature. It was also found that the optimum acrylonitrile concentration is 0.65mole/1. Acrylonitrile-grafted PET(AN-g-PET) film has a strong affinity for monovalent copperions. The PET film by graft polymerization with acrylonitrile is treated with copper compound, a reducing agent capable of reducing bivalent copper ions to monovalent copperions, and sulfur-containing compound so that the AN-g-PET film adsorbs monovalent copper ions and so that the adsorbed monovalent copper ions are converted into Cu2-xS. In the Cu2-xS-AN-g-PET film, vacant copper ion lattice points serve as the acceptor. The treated PET film had a metallic luster and its electrical resistivity was found to be 0.6$ imes$103( -cm).