PURPOSE: To securely conduct a high-speed clear marking by a method wherein the desired marking is conducted by projecting laser beam of specified wavelength onto the body surface to cause physical and chemical changes on the surface.

CONSTITUTION: A core wire 1 delivered from a core wire feeder 2 is applied with an insulating coating by an insulating coating extruder 3, and the insulated wire 4 is taken up by a winder 5 after being subjected to marking. The laser beams 8 emitted from a laser device 6 under the control by a controller 7 are focused on the body (wire 4) through a slitter 9 and a focusing device 10. The slitter 9 is a film for obtaining the light flux in the shape of the characters, figures and the like to be marked. The laser device 6 must be able to generate sufficient energy for causing heating, decoloration, deformation, chemical change and the like on the surface of the body, thereby achieving the desired marking.