NOVELTY - The plasma reactor (3) is used for purification of nitrogen oxide. The reactor is accommodated with ferroelectric substance pellet of preset diameter and internal electrode. Waste gas is made to flow into the reactor. Nitrogen monoxide contained in the gas is converted into nitrogen dioxide. Atmospheric pressure low-temperature non-equilibrium plasma is generated by applying voltage to the reactor at preset condition. Subsequently, the waste gas is reacted with reducing-agent solution, to remove nitrogen compound in waste gas.    USE - For purifying nitrogen oxide in waste gas.    ADVANTAGE - The nitrogen oxide in waste gas is efficiently and economically removed with suppressed consumption energy and suppressed production of byproduct.    DETAILED DESCRIPTION - The plasma reactor which generates atmospheric-pressure low-temperature non-equilibrium plasma is used for purification of nitrogen oxide. The plasma reactor is a container which is accommodated with pellet form ferroelectric substance which consists of barium titanate. An internal electrode is wired in the container. An external electrode is provided at the outer periphery of the container and connected with alternating current power supply (9). The diameter of the ferroelectric substance pellet is 3 mm or more. The waste gas with initial-stage concentration of nitrogen monoxide of more than 100 ppm, is made to flow into the reactor. The nitrogen monoxide contained in the waste gas is converted into nitrogen dioxide. Atmospheric pressure low-temperature non-equilibrium plasma is generated, when the voltage applied to the reactor is set to maximum value based on the generation amount of nitrogen dioxide. The waste gas after passing through the reactor is made to react with a reducing-agent solution, to remove nitrogen compound in waste gas. Thus, nitrogen oxide is purified.    An INDEPENDENT CLAIM is included for purifier (1) of nitrogen oxide.    DESCRIPTION OF DRAWING(S) - The figure shows the outline block diagram of the purifier.    Purifier (1)    Compressor (2)    Plasma reactor (3)    Power supply (9)    Air dryer (11)