The present invention provides a method and a machine for marking an electric cable that comprises a conductive core, an insulating coating, and a varnish comprising an outer layer and an inner layer of contrasting colors, with the marking being performed by ablating the outer layer of said varnish with a laser, the outer layer of varnish being based on polytetrafluoroethylene and being 10 .mu.m to 20 .mu.m thick. According to the invention the machine comprises:a pulsed CO.sub.2 laser (2) whose power is adjusted to obtain an energy density lying in the range 8 J/cm.sup.2 to 15 J/cm.sup.2 at the outer layer of the cable varnish;drive means (9) for driving the cable (4) so as to cause it to run past the laser beam (5);guide means (13, 14, 15) for guiding the cable (4) in the vicinity of the point of impact of said beam (5) on the cable; andcomputerized control means (6).