Laser machining apparatus

A laser machining apparatus comprising:

• a chuck table having a holding face adapted to hold a workpiece;
• laser beam irradiation means having an objective condenser lens adapted to condense and irradiate a laser beam onto the workpiece held by the chuck table;
• interferometric height position detection means adapted to detect a height position of an upper face of the workpiece held by the chuck table based on the interference between light reflected from the upper face of the workpiece and reference light;
• condensing point position adjustment means adapted to move the objective condenser lens vertically relative to the holding face of the chuck table;
• control means adapted to control the condensing point position adjustment means based on the height position of the upper face of the workpiece detected by the interferometric height position detection means;
• and
• confocal optical height position detection means adapted to detect the height position of the upper face of the workpiece held by the chuck table,
• wherein the control means specifies, as a correction value, the difference between the two height positions of the upper face of the workpiece held by the chuck table, one detected by the confocal optical height position detection means and another detected by the interferometric height position detection means, and
• the control means controls the condensing point position adjustment means based on the height position obtained by correcting the height position of the upper face of the workpiece detected by the interferometric height position detection means using the correction value.