PURPOSE: To prepare a simply designed multilayer interconnection board capable of mounting a high output integrated circuit (IC) by forming not only a multilayer circuit on an aluminum nitride substrate but also a metal conductor on an IC mounting circuit to thereby allow direct mounting of the high output IC.

CONSTITUTION: A conductor layer is formed on the surface of an aluminum nitride sintered body 1. The conductor layer includes a wiring part 2a and a die attaching part 2b. Then, a polyimide film 3 is formed. This polyimide film 3 is formed by subjecting the body to the process steps of: coating a photosensitive polyimide precursor varnish on the surface of the aluminum nitride sintered body 1 including the conductor layer parts 2a, 2b; exposing a predetermined part of the photosensitive polyimide precursor varnish using a glass mask; developing this in a predetermined developing solution to obtain a via hole pattern 4; and then heating the obtained member. By repeating these process steps, a multilayer circuit with as many layers as desired can be formed.