A laser beam machining process and apparatus, applicable to laser beam perforation and cutting, in which a laser beam is directed onto a wall (4) of a component (6) to be machined from one side of the said wall and emerges on the other side thereof following the machining operation. According to the invention, a disk (16) which is opaque to the laser beam is placed on the other side of the wall on the path followed by the laser beam when it emerges and performs a rotary movement, so as to stop the emerging laser beam and in this way protect the walls (8) adjacent to the machined wall against the impacts of the emergent laser beam.