PURPOSE: To enable even a relatively large electronic circuit to be developed relatively easily by achieving even a complex wiring connection efficiently with a configuration such as multilayered wiring layer, etc.

CONSTITUTION: A multi-chip module 1 consists of a module substrate 3 and a total of five chips 5 which are mounted on the module substrate 3. A module pad 10b which is provided on the module substrate 3 is provided corresponding to a module pin, electrically connected, achieves connection with an outside of the multi-chip module 1, and also a module pad 10a which is a customized chip-mounting pad is provided on the module substrate 3. In this manner module substrate wirings 7 are made of wirings of wiring layers of a multilayer structure, namely wirings of standard wiring layers and those of custom wiring layers, thus enabling a relatively large-scale electronic circuit whose development becomes difficult with a monolithic integrated circuit to be developed relatively easily.