Relations between plasma characteristics and formation processes of carbon nanotubes (CNTs) are investigated in order to develop an effective method for producing CNTs using glow discharge reactive plasmas. The plasma generated by the radio-frequency (RF) discharge in a crossed magnetic field is found to be apparently localized around an RF electrode under a certain condition determined by the magnetic-field strength and mixed gas (CH 4+H 2) pressure. In this case, it is demonstrated that CNTs are most effectively produced on the RF electrode which is negatively self-biased and exposed to a strong plasma-sheath drop.