In order to form active sites for grafting amino groups, a predominant elimination of fluorine atoms from fluoropolymers such as poly(tetrafluoroethylene), ethylene-co-tetrafluoroethylene co-polymer (ETFE) and poly(vinylidene fluoride) was carried out using the plasma irradiation technique, and the possibility that amino functional groups could be formed on the fluoropolymer surfaces was investigated. The NH3 plasma irradiation led to considerable elimination of fluorine atoms from the fluoropolymers, as well as grafting of nitrogen functionalities. The formation of nitrogen-containing groups was strongly influenced by the magnitude of the W/FM parameter, and the NH3 plasma operated at a low W/FM parameter of 79 MJ/kg was found to be preferable for the surface modification process. XPS spectra for the NH3 plasma-modified surfaces showed that the NH3 plasma attacked predominantly CF2-CF2 sequences rather than CH2-CH2 sequences in the ETFE polymer. The primary amino groups formed on the ETFE film surfaces were determined by fluorescence measurements. The concentration of the amino groups formed on the surfaces was not constant but varied according to the W/FM parameter. NH3 plasma operated at a low W/FM parameter of 79 MJ/kg was found to be preferable in grafting amino groups on the ETFE film surfaces.