Removal of NO<FONT SIZE="-1">_X</FONT> has been studied using an intense pulsed relativistic electron beam (IREB). The chamber is 20 cm long, and is irradiated by the IREB of 2 MV or 8 MV with the pulse width of 50 ns (full width at half maximum: FWHM). With the initial NO concentration of 100 ppm and pressure of 120 kPa, &sim;50% of NO is removed by firing of 10 shots of IREB, yielding 5 ppm/shot. The NO<FONT SIZE="-1">_X</FONT> removal amount in one shot does not depend on the initial NO concentration and electron energy.