To provide a brush manufacturing method suitable for mass-production of brushes with which a brush of high quality can be produced by introducing each bundle of bristles into a handle injection molding die effectively.

A useful side end of each bundle of bristles 1 rounded by a tip rounding means so that the tips of all bundles have a uniform shape, and the bundle 1 is inserted to a transporting plate 15 with the useful end leading, cut into a specified length, and handed over from the transporting plate to a bundle fastening plate 18 so that the tight condition is generated. A series of bundle support processes to hand over bundles 1 from the fastening plate 18 to a molding die 10 are conducted for each of the bundles 1 having different height, repetitively, and in such a way that level difference is given, the bundles 1 having different heights are put compressedly in the molding die 10 fully in the condition that the useful side ends of the bundles 1 and the opposite side ends are protruded in alignment within the die 10.