A laser micro processing system based on a diode-pumped solid-state ultraviolet laser has been developed. The laser system consists of a diode-pumped short-pulse YAG laser oscillator in which a fourth harmonic ultraviolet laser (wavelength: 266 nm) is generated using a CLBO crystal. This micro processing system, which is the world's cutting-edge laser processing system employing a CLBO crystal, realizes the generation of a shorter wavelength and shorter pulse than those in conventional processing systems equipped with CO₂ laser or YAG third harmonic laser. Results of micro through-hole processing tests have verified that this system is capable of high quality processing with only a small heat affected zone and little processing debris. In particular, it has been demonstrated that this system is applicable for processing inorganic materials that have been difficult to process with conventional systems.