To provide a technology which allows a badly worn-out surface of a bucket, etc., to be easily and economically reinforced so that another function and an object of friction cannot be damaged.

Constitutionally, a reinforcing material more rigid than a metal surface is embedded for integration in a region, in which wear on the metal surface occurs intensively due to contact with an object to be treated or a rigid object, so that a surface of the reinforcing material can be made approximately flush with the metal surface. When a groove 9 is provided along an edge part 3 of a cutting edge 2 of the bucket and backfilled by welding, tungsten carbide grains 8 are infilled for curing with a molten metal 10 until a surface of the grains 8 is made approximately flush with a surface 6 of the cutting edge 2, so that the reinforcing material 4, whose surface is flush with the surface 6, can also be provided.