To restrict generation of chrome-lack layer on a polished surface of a weld-jointed part by so-called Bauschinger effect to restrict generation of rust in the polished surface of the weld-jointed part, and improve durability of a sink.
A top T of a sink cabinet W is jointed with the sink S by welding, and the weld-jointed part is polished with polishing belts K of different yarn counts a plurality of times in order from coarse polishing to finish- polishing. In polishing the plurality of times, cross polishing in which a running direction of the polishing belt crosses a weld direction of the weld-jointed part and same-direction polishing in which the running direction of the polishing belt is the same direction as the weld direction of the weld-jointed part are alternately conducted.
HATANO TOSHIO
UCHIKAWA SEIJIRO
EGUCHI AKIRA
