An electronic control device (ECU 2A), comprising: a circuit board (3A, 3B) including a substrate and an electrolytic capacitor (5A, 5B) connected to the substrate, the electrolytic capacitor having an outer peripheral surface; a heat sink including a recess that houses the electrolytic capacitor (5A, 5B), the recess having a side surface along the outer peripheral surface of the electrolytic capacitor (5A, 5B); and heat dissipation material provided in the recess, wherein the electrolytic capacitor (5A, 5B) has an end surface facing a bottom surface of the recess, and the heat dissipation material is in contact with: the end surface of the electrolytic capacitor (5A, 5B); the outer peripheral surface of the electrolytic capacitor (5A, 5B); a convex curved surface of the electrolytic capacitor (5A, 5B), the convex curved surface being a curved surface connecting the end surface and the outer peripheral surface; the bottom surface of the recess; the side surface of the recess; and a concave curved surface of the recess, the concave curved surface being a curved surface connecting the bottom surface and the side surface, the heat dissipation material being in a paste form is disposed in a gap between the electrolytic capacitor (5A, 5B) and the recess such that the gap has: a first width between the bottom surface of the recess and end surface of the electrolytic capacitor (5A, 5B); a second width between the side surface of the recess and the outer peripheral surface of the electrolytic capacitor (5A, 5B); and a third width between the concave curved surface of the recess and the convex curved surface of the electrolytic capacitor (5A, 5B), and each of the first width, the second width, and the third width is in a range between 0.5 to 1.5mm. a circuit board (3A, 3B) including a substrate and an electrolytic capacitor (5A, 5B) connected to the substrate, the electrolytic capacitor having an outer peripheral surface; a substrate and an electrolytic capacitor (5A, 5B) connected to the substrate, the electrolytic capacitor having an outer peripheral surface; a heat sink including a recess that houses the electrolytic capacitor (5A, 5B), the recess having a side surface along the outer peripheral surface of the electrolytic capacitor (5A, 5B); and heat dissipation material provided in the recess, wherein a recess that houses the electrolytic capacitor (5A, 5B), the recess having a side surface along the outer peripheral surface of the electrolytic capacitor (5A, 5B); and heat dissipation material provided in the recess, wherein the electrolytic capacitor (5A, 5B) has an end surface facing a bottom surface of the recess, and the heat dissipation material is in contact with: the end surface of the electrolytic capacitor (5A, 5B); the outer peripheral surface of the electrolytic capacitor (5A, 5B); a convex curved surface of the electrolytic capacitor (5A, 5B), the convex curved surface being a curved surface connecting the end surface and the outer peripheral surface; the bottom surface of the recess; the side surface of the recess; and a concave curved surface of the recess, the concave curved surface being a curved surface connecting the bottom surface and the side surface, the end surface of the electrolytic capacitor (5A, 5B); the outer peripheral surface of the electrolytic capacitor (5A, 5B); a convex curved surface of the electrolytic capacitor (5A, 5B), the convex curved surface being a curved surface connecting the end surface and the outer peripheral surface; the bottom surface of the recess; the side surface of the recess; and a concave curved surface of the recess, the concave curved surface being a curved surface connecting the bottom surface and the side surface, the heat dissipation material being in a paste form is disposed in a gap between the electrolytic capacitor (5A, 5B) and the recess such that the gap has: a first width between the bottom surface of the recess and end surface of the electrolytic capacitor (5A, 5B); a second width between the side surface of the recess and the outer peripheral surface of the electrolytic capacitor (5A, 5B); and a third width between the concave curved surface of the recess and the convex curved surface of the electrolytic capacitor (5A, 5B), a first width between the bottom surface of the recess and end surface of the electrolytic capacitor (5A, 5B); a second width between the side surface of the recess and the outer peripheral surface of the electrolytic capacitor (5A, 5B); and a third width between the concave curved surface of the recess and the convex curved surface of the electrolytic capacitor (5A, 5B), and each of the first width, the second width, and the third width is in a range between 0.5 to 1.5mm.