Abstract: The present invention provides a plasma reaction apparatus capable of producing ozone water, alkaline water, or acid water at a high efficiency and low power consumption during discharge in water. The invention also achieves a decrease in the molecular weight of oil in a short time through stable glow discharge during discharge in the oil. Accordingly, there is provided a plasma reaction apparatus for causing discharge to occur by using liquid such as water and oil, or gas as a medium and by applying a voltage to two electrodes disposed within a reactor. The apparatus comprises first and second electrodes formed on both sides with a discharge region interposed therebetween, and a reactive catalytic layer formed on at least one of the first and second electrodes that face the discharge region. The apparatus is effective in decomposition, purification and neutralization of harmful liquid and gaseous materials.