In a semiconductor laser module with an optical isolator where the form of a metal holder for holding a fiber stub varies, optical-isolator parts are miniaturized and unified, simplifying product management, reducing delivery time and cost. A fiber stub with an optical isolator is provided in such a manner that a stepped surface is formed on an end surface of a ferrule, where an optical fiber has been inserted and secured to a through hole formed at the center of the ferrule. The fiber stub is formed by attaching an optical isolator element composed of a polarizer and a Faraday rotator to the stepped surface.