Poly(ethylene terephthalate)(PET) tire cord has relatively lower adhesion properties caused by limited reacting sites. In order to improve the adhesion force between PET tire cord and rubber, an additional process to activate surface of PET has been employed. Atmospheric plasma was used to substitute the chemical finishing process of PET tire cord as a green dipping process. Contact angle was measured to confirm surface change of PET after plasma treatment. The treated PET tire cords with/without resorcinol-formaldehyde-latex(RFL) and unvulcanized rubber were vulcanized in a testing mold at $160^{circ}C$. After atmospheric plasma treatment of PET tire cord, adhesion force was somewhat increased under some conditions.