A starter drive device which drives a starter motor by, upon actuation of a starter switch, turning a starter relay ON and OFF via an electronic control device, wherein the electronic control device includes: an interface circuit; a power source control circuit; a calculation device and a delay circuit; a buffer; an addition circuit; a latch circuit; a first pull up circuit; a second pull up circuit; and wherein, if the power source control circuit has detected a drop of voltage of the power source when the starter motor is being driven, along with stopping the calculation device, the buffer disconnects the calculation device from the latch circuit, and controls the starter relay by operating the driver circuit via the latch circuit based upon the signals from the interface circuit and the second pull up circuit.