A process control apparatus controls a focus position of a laser beam, while a laser processing mechanism converges the laser beam into a predetermined focus position and performs a laser processing on a workpiece. The process control apparatus includes: a calculator that, based on the magnitude of an output of the laser beam that changes during the laser processing, calculates a change amount of a positional deviation of the focus position in an optical axis direction that changes during the laser processing at a laser beam radiation position; and a control unit that, based on the change amount of the positional deviation that has been calculated by the calculator, controls the focus position of the laser beam during the laser processing so as to resolve the positional deviation of the focus position.