The invention provides a bleaching method of natural fibers. By the invention, it is possible to bleach raw cotton fibers without dewaxing. The method of the invention is to bring the natural fibers on each of which wax adhere, into contact with water solution containing hydroxy percarboxilic acid for bleaching. The natural fibers may be raw cotton fibers. The hydroxy percarboxilic acid may be perlactic acid. The water solution may contain hydroxy carboxilic acid, hydrogen peroxide and alkali agent with hydroxy percarboxilic acid.