Abstract: A surface treatment process for improving surface properties of a timber as to wetness by exposing the timber to a plasma mixture of an inert gas and a reactive gas at a near atmospheric pressure. Prior to being exposed to the plasma mixture, the timber is treated to reduce a moisture content below a fiber saturation point of the timber so as to eliminate free moisture from the fibers of the timber which would otherwise lead to unstable plasma and therefore detract an uniform improvement over substantially the entire surface expected at the subsequent exposure to the plasma mixture. Thus, the plasma treatment can be effected in the absence of the free moisture to obtain a desired surface improvement uniformly across the surface of the timber, which gives an enhanced practicability of improving the surface properties of the timber, in addition to that the plasma mixture is generated at near the atmospheric pressures readily available without requiring substantial vacuum generating equipments.