In an electronic device, a heat generation part pattern is connected to a heat generating element to heat from the heat generating element. A temperature detecting element is disposed adjacent to a first surface of a substrate. A direct under layer pattern is disposed on a second surface of the substrate opposite to the temperature detecting element in an area including a portion corresponding to the temperature detecting element. An interlayer connection pillar connects between the heat generation part pattern and the direct under layer pattern to conduct heat. The heat generated from the heat generating element is effectively conducted to the temperature detecting element through the heat generation part pattern, the interlayer connection pillar, and the direct under layer pattern, and thus the temperature detecting element accurately detects the temperature of the heat generating element.