To reduce the remaining force on a sheet surface by forming the groove of a valve plate in a non-restricted flat form, a hard alloy of one layer and one pass type is layed and raised on a part of the groove on which it is layed with the weeping width of welding torch being widened, and thereafter cutting and polishing the part, thereby forming the sheet surface.

One pass with the slightly shorter weeping width W of a torch 4 than a bead width B (raised width) is formed in one layer by moving the torch 4 to a specified distance right and left from the center thereof. In the case of one pass with the weeping width W being made large, it is solidified in its dia. direction being different from the case where the weeping width W of the torch 4 is reduced for every pass and metal is layed and raised in the circuferential direction. In this case of one pass, the solidification of raised part in a groove starts according to the movement of the torch 4 and the flow of molten metal stops in a relatively narrow range. Since the flow of molten metal reduces the ratio gradually according to the increase in the beat width B. a flat shape of groove is required. Accordingly, the residual stress on a sheet surface 1 can be reduced.