Laser processing device and laser processing method

A laser processing method comprising:

• irradiating, with a laser light, a surface of a steel sheet being conveyed in a predetermined conveyance direction, using a laser light source;
• stirring up, from the surface of the steel sheet, laser spatter generated from an irradiation site by injecting a first gas in parallel with an optical axis direction of the laser light toward the irradiation site of the laser light, using a gas injector;
• collecting the laser spatter via a dust collection port of a dust collector provided at either an upstream side or a downstream side of the irradiation site in the conveyance direction;
• and
• boosting a suction flow of the laser spatter toward the dust collection port by supplying a second gas between a gas supplier and the steel sheet using the gas supplier disposed at an opposite side of the laser light source from the dust collector in the conveyance direction.