To make the brush out of polyacetal resin, within which a hollow part is present, which is excellent in dimensional accuracy and has reduced weight of parts, the number of parts and assembling manhours by a method wherein the brush consists of a plate-like part, the minimum thickness of which lies in a specified range, and a supporting part, which is integral with the plate- like part.

A brush having a plate-like part, thickness of which lies in a range of 0.2-1.5mm and the size of which is about 200×12mm2, and a supporting part, the shape of which is a circle having the diameter of about 4mm and the length of which is about 220mm is molded by an injection blow molding method out of polyacetal resin or tenac-C 7520. Thus, a brush made only of resin, the plate-like part of which is excellent in flatness and surface appearance, which has no warpage, and is excellent in dimensional accuracy and has a few assembling manhour.