A laser beam processing machine comprising a laser beam application means for applying a laser beam to the top surface of the workpiece held on the chuck table, the laser beam application means comprising a processing laser beam oscillation means for oscillating a processing laser beam and a condenser for converging the processing laser beam oscillated by the processing laser beam oscillation means, wherein the laser beam processing machine further comprises a focal point position adjusting means for adjusting the position of the focal point of the processing laser beam converged by the condenser, a height position detection means for applying a detection laser beam to the workpiece through the focal point position adjusting means to detect the height position of the top surface of the workpiece based on its reflected light, and a control means for controlling the focal point position adjusting means based on the detection value of the height position detection means.