a laser beam heat treatment for a metal wire has improved incidence and processing conditions so as to achieve efficient surface heat treatment with a circumferentially averaged laser beam flux and with remarkably enhanced fatigue strength in a high speed heat treatment . the method and apparatus is characterized by forming a cone shaped mirror of circular or polygon cross section having a peak angle in a range of 5 ° to 20 ° and interior mirror surface , the cone shaped mirror defining an opening having a diameter greater than the diameter of the metal wire in a range of 0 . 2 to 2 mm , feeding the metal wire having a diameter less than or equal to 1 mm through the cone shaped mirror along the center axis thereof , irradiating a laser beam with an incident angle including an angular deflection with respect to the center axis of the cone shaped mirror in a range of ± 10 ° resulting in multiple reflection of the laser beam between the interior mirror surface and the surface of the fed metal wire .