Process control device and laser processing

Process control device that controls a focal position of a laser beam during a laser processing apparatus converges the laser beam onto a predetermined focus position, and performs laser processing on a workpiece, wherein the process control device comprising: a calculator which, based on a magnitude of an output of the laser beam changes during the laser processing, calculates a change amount of a position deviation of the focus position in an optical axis direction which varies as a laser beam irradiation position during the laser processing; and a focus position controller which, based on the change amount of the positional deviation, which is calculated by the calculator, the focus position of the laser beam during laser processing so controls that the positional deviation of the focus position is terminated.