To enhance an operation efficiency of both surface machining with no necessity that a plate material is returned to an original position and an inversion of an upper and lower surfaces of a plate-like material is also carried out by a manual operation by providing an inversion device for reversing operation by providing an inversion device for reversing operation by providing an inversion device for reversing the upper and lower surfaces of the plate-like material between a plurality of boring devices disposed along a conveying direction.

Each boring device 10, 11, 12 of the machining device 1 is provided with a belt conveyor 20 for conveying a subject to be processed to a machining table and a processing head 50. After an upper surface of a panel 3 thrown from a throwing machine 2 is processed by a boring device 10, it is reversed by an inversion device 100 and a lower surface is machined by the device 11. After the panel 3 is processed by a boring device 12, it is loaded in a loading machine 15 through a belt conveyor 14. In the case where it is not necessary that the panel 3 machined by the boring device 10 is reversed, it is passed through the inversion device 100 as such. In this case, a processing time can be shortened by dividing machining among boring devices.