Provided is a resin-sealed electronic control device reduced in size, which includes a double-sided mounting board as at least one of a plurality of electronic boards obtained by division so that a large mounting surface with a small plane area is ensured. Each of a first electronic board (30A) and a second electronic board (40A) bonded onto an upper surface and a lower surface of each of a pair of separate beam members (20A) includes two surfaces on which outer circuit components (31, 32, 41, 42) and an inner circuit component (33, 43) are respectively mounted. A height of each of the inner circuit components is equal to or less than a thickness of each of the separate beam members (20A). Heat-generating components (32, 42) in the outer circuit components are provided to be adjacent to and opposed to the separate beam members (20A).