Distance P' between the centers of an outermost through hole (4b) and an adjacent through hole (4d) closest thereto is set greater than the distance P between the centers of a central through hole (4a) and an adjacent through hole (4c) closest thereto. Since the quantity of solder filling the side apart from the center of a case increases in the outermost through hole (4b) when an electronic component is mounted, a stress generated when the lead of the electronic component is bent due to difference in thermal expansion coefficient between the electronic component case and a multilayer circuitboard (1) during soldering process is absorbed by the solder. Consequently, it is possible to prevent through hole corner crack and stripping of the through hole.