PURPOSE: To mount properly a necessary component and so on in the small internal capacity of a casing and to contrive a reduction in the size of a product and a decrease in the weight of the product by a method wherein a circuit pattern consisting of a metal thin layer is formed on the inner surface of a substrate made of Al through an insulating layer.

CONSTITUTION: The original form of a desired circuit pattern is formed on a copper foil 3 of a substrate 4 formed by adhering the copper foil 3 on the surface on one side of an Al base 1 through an insulating layer 2 by a resist printing or the like. Then, a protective film 5 is adhered on the surface of the base 1 and unnecessary parts of the foil 3 are removed by etching to form a circuit pattern 6. The substrate 4 provided with its outside subjected to surface treatment and provided with the pattern 6, on which a prescribed component is mounted, formed on its inner side is subjected to press working and is used as a casing 9, in which the desired circuit pattern 6 is formed. Thereby, there is no need to house a printed substrate and so on separately in its interior. Accordingly, the internal capacity of the casing 9 can be remarkedly made small.