An electronic control apparatus can be reduced in size and cost by removing a metal substrate part. The apparatus includes a housing having a pair of opening portions at its opposite sides, a heat sink attached to one of the opening portions of the housing, a pair of semiconductor switching elements mounted on the heat sink, a circuit board arranged in opposition to the heat sink, a plurality of conductive plates electrically connecting the circuit board and the semiconductor switching elements to each other, and a plate spring urging the semiconductor switching elements against the heat sink. The plate spring has engagement portions press-fitted to and engaged with inner sides of holding portions which are formed on the housing, and the housing has engagement portions engaged with protruded portions of the heat sink.