To reduce a treatment cost and to reform the portion of a metal by using a retaining plate of the same material as a base metal or the material different therefrom, fixing an additive material for reforming to the base metal surface and subjecting the material to heating and remelting.

When, for example, the aluminum base metal A5052 is reformed, a copper pipe cut to a prescribed length is used for the additive material 3 for reforming and this copper pipe is inserted into the groove of the retaining plate 2 made of a sheet of the same material as the material of the base metal and is fixed to the prescribed reforming position of the base metal. The base metal surface is then heated and remelted by irradiation with high-density heat energy, by which the partial reforming of the base metal is executed. A nickel wire cut to a prescribed length is otherwise used for the additive material 3 and is inserted into the groove of the retaining plate 2 made of a sheet of C1010 material and is subjected to heating and remelting. As a result, the effect of only the component of the additive material 3 suffices in the case of the retaining plate 2 of the same material as the material of the base metal. In the case of the retaining plate 2 of the different material, the component thereof acts effectively for reforming as well.