The kinetics of intercalation of halogen molecules Br2or ICI into pyrolytic graphite “NIKAFILM”, a commercial product of Nihon Carbon Inc., has been studied by the measurement of electron transport phenomena, especially the thermoelectric properties. The data were analyzed by a two-carriers band model, and it was concluded that the change in the resistivity and Seebeck coefficient is due to the increase in the positive hole density because the intercalant halogen molecules work as acceptors. From the weight increment the stage index was tentatively estimated to be four, and the deduced charge transfer rate was 1.33 × 10−4e/mole-cule.