An atmospheric pressure glow discharge plasma treatment method, in which a gaseous mixture comprising argon, argon and helium, or argon and hydrogen, mixed with water vapor or water vapor and ketones at room temperature or a specified temperature, is introduced into a plasma reactor having a dielectric-coated electrode comprising a solid dielectric disposed on the surface of at least one of opposing electrodes, and a high-frequency voltage is applied under atmospheric pressure to generate atmospheric pressure glow discharge and excite a plasma, thereby making surface treatment of plastics or fibers disposed between the electrodes.