The important accidents that the diagonal members of the steel truss bridge have broken due to severe corrosion damages occurred recently. Therefore it is expected to establish the rational and efficient maintenance management technique depending on the bridge type and structure characteristic. Especially, the corrosion damages of the main members may have a serious influence on the safety of the bridge system, and the technique for the investigation and checking is appropriately demanded. In this study, for the corroded gusset plate connection which was cut out from the steel truss bridge, we measured the corrosion shape in detail using the surface roughness measurement equipment, and evaluated the actual state by the surface corrosion of the outside and the narrow inside of the gusset plate connection.
