A laser processing system capable of reliably determining an abnormality in a jet during laser process. The laser processing system comprises a nozzle including an emission opening configured to emit a jet of an assist gas along an optical axis of a laser beam, the nozzle being configured to form a maximum point of velocity of the jet at a position away from the emission opening; a measuring instrument configured to measure any of the velocity of the jet and a sound generated by the jet impinging on a workpiece; and an abnormality determination section configured to determine whether or not output data of the measuring instrument is different from reference data.