NOVELTY - A plasma reaction apparatus comprises hollow furnace having discharge opening (62) at an upper position of the furnace, for discharging a plasma reactant; raw material inflow pipe connected to a lower part of the furnace so that a raw material for a plasma reaction is supplied to the inside of the furnace, and includes an intake opening in the furnace; and electrode (70) which is put through a bottom of the furnace and is spaced from an inner wall of the furnace.    USE - For reforming of fuel and chemical treatment of persistent gas.    ADVANTAGE - The apparatus enables a raw material to be sufficiently reacted within a plasma reaction space having a restrictive volume and enables a high plasma reaction to be faster performed. A plasma reaction zone is expanded to temporarily stay before it is discharged, thus excluding the discontinuity of the plasma reaction zone.    DETAILED DESCRIPTION - The plasma reaction apparatus comprises hollow furnace having discharge opening at an upper position of the furnace, for discharging a plasma reactant; raw material inflow pipe connected to a lower part of the furnace so that a raw material for a plasma reaction is supplied to the inside of the furnace, and includes an intake opening in the furnace and formed to be tilted at a predetermined angle to a normal direction of an outer circumference surface of the furnace, so that the raw material being supplied forms a rotating flow and progresses inside the furnace; and electrode which is put through a bottom of the furnace and is spaced from an inner wall of the furnace at a predetermined interval, so that a discharge voltage is generated for the plasma reaction for the raw material being supplied to the inside of the furnace. The furnace includes a section positioned above the electrode and expanded in width, so that a broad area chamber is formed to expand a plasma reaction zone to be temporarily stayed in the broad area chamber when the raw material being supplied to the furnace makes the plasma reaction. INDEPENDENT CLAIMS are included for:    (1) a plasma reaction method using the plasma reaction apparatus;    (2) a plasma reactor; and    (3) an apparatus for decreasing nitrous oxides.    DESCRIPTION OF DRAWING(S) - The figure is a sectional view of the plasma reactor.    Tank (50)    Body (60)    Furnace (61)    Discharge opening (62)    Mixing chamber (67)    Electrode (70)