An electronic part-incorporated multilayer substrate is provided. The multi-layer substrate includes a core formed with a plurality of holes capable of containing an electronic part, a bottom insulating resin layer formed on a bottom surface of the core, a top insulating resin layer formed on a top surface of the core, a wiring layer selectively formed on an outer surface of the bottom insulating resin layer or top insulating resin layer, and an electronic part contained in any of the holes.
Both of the bottom and top insulating resin layers have a structure that is a combination of a resin which is changed to cohesiveness when heated and which undergoes smaller plastic deformation when heated to a higher temperature and an insulating resin layer which has a thickness sufficient to maintain insulation between the electronic part or a conductor of the core and the wiring layer and which inherently undergoes small plastic deformation. Thus, the electronic part can be securely and sealed in the hole without using an adhesive separately.