The invention discloses a laser focus dynamic machining method and device, and belongs to the technical field of laser machining application. According to the basal principle of the laser focus dynamic machining method, in the machining process of laser drilling, cutting, welding, etching and heat cracking separating, a laser focus is no longer fixed in a position to be motionless, and the laser focus moves downwards or upwards in the direction of optical axis of the thickness of a workpiece to be machined at the certain speed, or the laser focus vertically moves in a linear or swinging or spiral mode at the certain frequency. By means of the laser focus dynamic machining method and device, the serial processing problems caused by nonuniform energy density distribution of the laser optical axis in a traditional machining mode are overcome.