PURPOSE: To permit the easy adhesion of face plates and to produce an L-shaped panel in a line by projecting the ends of the face plates in the form of lap pieces from one end of panel frames and pressing the same to the end faces of the panel frames of a main panel.

CONSTITUTION: The panel frames 1, 4 are respectively manufactured by framework and thereafter the face plates 2, 5 are adhered respectively to the outside flank of the frame 1 and the outside flank of the frame 4. The face plate 5 is adhered to the frame 4 to manufacture an end panel 6. After a main body panel 3 and the end panel is manufactured, the end face of the panel frame 4 of the panel 6 on the side where the lap piece of said frame is projected is butted to the inside flank at the end of the frame 1 and the rear side of the lap piece of the plate 5 is pressed to the end face of the panel frame 1 of the main panel 3. The butt parts of the frames 1, 4 are bound and fixed by bolting or welding, by which the L-shaped panel is obtd.