Abstract: Method and apparatus for the surface-hardening treatment of a synthetic resin article is provided, wherein the article is brought into countercurrent contact with a freely falling liquid film of a surface-hardening solution while the article is gradually pulled up thereby to be coated with the surface-hardening solution, and then, the coated article is irradiated with ultraviolet rays to cure the coating. The article is conveyed to a hardening solution tank by a first conveyor where the surface-hardening solution is caused to flow down on downwardly inclined liquid film guide plates attached to the hardening solution tank, at a flow rate of 2 to 15 ml/sec.multidot.cm of the width of the guide plate. The countercurrent contact of the article with the liquid film is initiated at a point 3 to 30 mm apart from the flow-out end of the guide plates. The hardening solution is circulated to effect the temperature adjustment and filtration.