There is provided an electronic control unit including: input terminals connected to output terminals of a magneto generator driven by an engine; DC output terminals; a control power supply circuit that converts an AC voltage input between the input terminals into a DC voltage equal to a set value; and a microprocessor that controls electrical components of the engine, wherein the electronic control unit further includes an interruption signal generation circuit that compares an output voltage of the control power supply circuit with a certain abnormality determination voltage and generates an interruption signal when the output voltage of the control power supply circuit becomes the abnormality determination voltage or less, and an abnormality state storage unit for storing that an abnormality occurs in a power supply portion when the interruption signal is generated.