The decomposition of bromomethane (CH3Br), which is one of ozone-depleting substances (ODSs), is carried out using a pulsed dielectric barrier discharge. The plasma reactor consisting of a stainless discharge wire electrode and quartz cylinder wrapped by a copper mesh as the ground electrode is employed. This reactor is supplied by a pulsed high-voltage power supply using an insulated-gate bipolar transistor (IGBT). The effects of humidity, a flow rate, and an initial concentration on CH3Br decomposition are investigated. As a result, the relative humidity slightly affects the CH3Br decomposition. The CH3Br decomposition efficiency decreases with an increase in gas flow rate; however, the amount of decomposed CH3Br increases with gas flow rate. More than 95% of CH3Br decomposition efficiency is achieved at the gas flow rate of 1 L/min and initial CH3Br concentrations of 1000 ppm, 5000 ppm and 1%. By GCMS analysis, it is shown that approximately 95 % of the decomposed CH3Br is converted to HBr, which can be removed easily by an alkali scrubber. The energy efficiency of CH3Br decomposition increases with the initial concentration at the same specific energy. In addition, the specific energy can be decreased with the energy efficiency maintained by increasing a gas flow rate.