Plasma irradiation of solid surfaces increases its wettability significantly and this phenomenon can be used to enhance phase change heat transfer. To obtain the fundamental data for utilization of plasma irradiation in heat transfer enhancement, the relation between irradiation time and contact angle was obtained. Copper, aluminum and stainless steel are used as the test materials. Each sample surface was finished with emery papers and polishing powder. The effect of surface roughness on contact angle of plasma-irradiated surface was examined. As the irradiation time of plasma increases, the contact angle decreases. The terminal contact angles are 11°, 3° and 6° for copper, aluminum and stainless steel, respectively. Aluminum is the best material among three metals. The immersion cooling experiment has also been, conducted to reveal the effect of plasma irradiation on enhancement of cooling velocity and it was found that the metal irradiated by plasma was cooled down more rapidly than non-irradiated metal.