An internal combustion engine controller has: a voltage booster circuit for boosting a battery power source; a booster side driver element for flowing a current through the injectors by using the boosted voltage; a battery side driver element disposed in parallel with the booster side driver element to flow a current through the injectors by using the battery power source; a first downstream side driver element provided by controlling currents flowing through the injectors; current regeneration diodes for flowing currents from the downstream side to the upstream side of the injectors; a booster side current detector resistor for detecting currents flowing via the current regeneration diodes; and an injector control circuit for controlling and driving the booster side driver element, battery side driver element and first downstream side driver element.