An engine control unit for controlling an automobile engine, which is equipped with a booster circuit for boosting the voltage of battery power source, an injector driving circuit for driving an injector by making use of a boosted high voltage, and a microcomputer for controlling the engine; wherein the engine control unit is featured in that an LC module mounted with a booster coil constituting the booster circuit and with an electrolytic capacitor, a power module mounted with a rectifying device constituting the booster circuit and the injector driving circuit and with a switching device, and a control circuit board mounted with the microcomputer and with a connector acting as an interface for an external member of the engine control unit are laminated each other. The power module is partitioned into at least two portions and fixedly contacted, through a heat radiation part, with a housing cover, and heat radiation fins are arranged on an outer surface of the housing cover where the power module is disposed.