An electronic control device 1 includes: a circuit board 4 having a first surface 4A on which heat-generating components 21, 22, 23 and heat-degradable components 31, 32 are mounted; a first metallic case 2 covering the first surface 4A; a second case 3 covering a second surface 4B of the circuit board 4 opposite to the first surface 4A; supporting members 51, 52 provided between the heat-degradable components 31, 32 and the first case 2 to support the heat-degradable components 31, 32; and heat-dissipating members 41, 42, 43, each provided on at least any of the heat-generating components 21, 22, 23, and the first case 2, to transmit heat generated from the heat-generating component 21, 22, or 23, to the first case 2. A heat conductivity of the heat-dissipating members 41, 42, 43 is higher than a heat conductivity of the supporting members 51, 52.