LASER PROCESSING METHOD

The present invention relates to a laser processing method that is capable of performing high-throughput processing by using an inexpensive pulsed laser light source. A pulsed laser light source 1 that is favorably used in this laser processing method has a seed light source, an amplifying optical fiber, a bandpass filter and the like, as well as a MOPA structure. The laser processing method is a method of processing a metal thin film formed on a transparent substrate by radiating pulsed light onto the metal thin film, and has the steps of repeatedly outputting the pulsed light by directly modulating a semiconductor laser of the seed light source in accordance with electric signals, amplifying the pulsed light using an optical amplifier including an optical amplification medium, controlling the full width at half maximum of the pulsed light that is amplified and outputted by the optical amplifier to be 0.5 ns or shorter, and removing the metal thin film by radiating the pulsed light thus having the controlled full width at half maximum onto the metal thin film through the transparent substrate.