To provide a laser beam-machining device in which the adhesion by being molten to a chuck table of an adhesive tape to which materials to be worked such as a wafer are stuck is prevented.

This device is a laser beam-machining device which has the chuck table having a holding surface for holding the wafer and a laser beam irradiating means with which the wafer held with the chuck table is irradiated with the laser beam. The device is provided with a protective sheet laying means which is mounted to the chuck table and has the protective sheet for covering the holding surface.