A method of manufacturing a circuit apparatus includes forming a plurality of pierced holes in a metal substrate. A first wiring layer is formed on one side of the metal substrate via a first insulating layer, and a second wiring layer is formed on the other side of the metal substrate via a second insulating layer. A conductor layer is formed in at least some of the plurality of pierced holes to establish a connection between the first wiring layer and the second wiring layer. A circuit element is connected to the first wiring layer on the one side of the metal substrate. When a plurality of pierced holes are formed, protrusions are formed on a surface of the metal substrate at least along either edge of each of the pierced holes provided with the conductor layer to protrude in a convex manner from the surface of the metal substrate.