To obtain a metal core substrate having a small thermal influence on a mounting part, a long lifetime, high reliability and a high accuracy.

The metal core substrate includes a first insulating layer 1, a conductor layer 2 for grounding, a second insulating layer 4 having a part mounting surface to be mounted with the part, such as a semiconductor element, etc., and a laminate 3 in which a high thermal conductivity layer 3a produced by a substance having a high thermal conductivity and a low thermal conductivity layer 3b produced by a substance having a low thermal conductivity are alternately laminated between the first insulating layer and the conductor layer, so that the laminating direction of the laminate 3 becomes perpendicular to the thickness direction of the first insulating layer. The high thermal conductivity layer may be formed of an aluminum, and the low thermal conductivity layer may be formed of an epoxy resin.