Disclosed herein are a heat-radiating substrate and a method of manufacturing the same. The heat-radiating substrate includes: a core layer including a core metal layer and a core insulating layer formed on the core metal layer and divided into a first region and a second region; a circuit layer formed in the first region of the core layer; a build-up layer formed in the second region of the core layer and including a build-up insulating layer and a build-up circuit layer; an adhesive layer formed between the second region of the core layer and the build-up layer; and an impregnation device mounted on the build-up layer to be impregnated into the adhesive layer. A heat generating element is mounted on the circuit layer and a thermally weakened element is mounted on the build-up layer, thereby preventing the thermally weakened element from being damaged by heat of the heat generating element. The impregnation device is formed on the build-up layer and is impregnated into the adhesive layer, thereby efficiently utilizing a space.