First and second metal foil layers are laminated on opposite surfaces of a
first insulating layer to form a first board. Then, the first and second metal
foil layers are formed into predetermined conductor patterns respectively. Then,
second and third insulating layers of second and third boards formed separately
from the first board are laminated on the first and second metal foil layers through
first and second adhesive layers respectively. Then, a thin layer portion is removed
and thick layer portions are formed into predetermined conductor patterns respectively
in third and fourth metal foil layers of the second and third boards.
