We have fabricated electrodes for a supercapacitor using fluorinated single-walled carbon nanotubes (SWCNTs). Although the specific surface areas of the pristine and fluorinated SWCNTs are similar, the electrochemical reactions are different significantly from each other. The specific capacitance of the fluorinated SWCNTs is smaller than that of the pristine sample particularly at large discharge current density, which can be attributed to the micropores formed during fluorination. After heat treatment at 900 degreesC for 30 min, the nonredox reaction is dominant, and furthermore, the fluorinated sample gives a larger specific capacitance than the pristine sample.