In this study, the wetting time measurement of five weathering plates, which have three types of chamfered edges, were carried out for clarifying the superiority of drainage performance. The wetting state on steel surface was judged by measuring the electrical resistance at a center point near the plate edge. The inclination of all specimens was set to 2 % in this wetting time measurement. The protective rust (about 70 μm thickness) was generated all over the surfaces of specimens by the outdoor exposure test. From the experimental results, the linear-chamfered edges could shorten the average wetting time by 14~28 % than the non-chamfered edge, because the water-drops attached to the edges drip more easily. On upper surface, the drainage performance will be significantly influenced by the cutting size of chamfered edges.