PURPOSE: To acquire an electronic part mounting substrate of great junction strength and good heat dissipating properties by joining a side of a stud base to a heat sink by solder.

CONSTITUTION: A heat sink 1 is provided to an insulating base material 9, and a stud 2 for attaching a fin is fixed to the heat sink 1. A side of a base 22 of the stud 2 is joined to the heat sink 1. A periphery of the base 22 is enclosed with solder 15 and solder is joined firmly to the heat sink 1; therefore, the stud 2 and the heat sink 1 are made firmly integrat and provided with high junction strength. An electronic part mounting substrate of good heat dissipating properties can be acquired in this way.