Abstract: An electronic component mounting board includes a substrate having an electronic component mounting opening formed in an upper surface thereof and a recess provided on a rear surface thereof larger in size than the electronic component mounting opening; a heat radiating plate fixed to the recess by bonding material with a position of an upper surface of that heat radiating plate exposed to the electronic component mounting opening; an exposed depression extending over the substrate and the heat radiating plate at a position where a side wall of the recess and a side wall of the heat radiating plate confront each other and having a part of the bonding material exposed flush with a bottom surface thereof; and a metal plating layer continuously covering in sequence a lower surface of the heat radiating plate, a surface of the exposed depression and a rear surface of the substrate. A method of manufacturing the aforesaid electronic component mounting board is also set forth.