PURPOSE: To heighten the designing effect and to enable mass production, by slicing a foam body having numerous bubbles to form a platy body having numerous perforated apertures and a thickness smaller than the sizes of the bubbles.

CONSTITUTION: A foam body 2 having numerous bubbles 1 is sliced to form a platy body 4 having numerous perforated apertures 3 and a thickness smaller than the diameters of the bubbles. An aluminum foam is used as the foam body 2, and the diameters of the bubbles 1 are approximately 2-7 mm. The thickness of the platy body is approximately 3-5 mm. The less the thickness of the sliced platy body 4 is, the more an aperture ratio representing the ratio of the area of the apertures 3 to the whole area of the platy body 4 can be. Therefore, the aperture ratio can be easily controlled by the slicing thickness. Thus, the designs full of variety can be obtained, also they can be easily mass- produced because of the slicing.