Provided is a highly reliable electronic control unit capable of improving responsiveness of an output current of a switching power supply to load current variation and suppressing power supply voltage variation accompanying the load current variation at low cost and with high power efficiency. Provided are: a calculation unit that performs signal processing; a first power supply circuit that supplies a first power supply voltage to the calculation unit; and a second power supply circuit that supplies a second power supply voltage to the first power supply circuit. The calculation unit has a function of outputting a control signal when a change in a consumed current of the calculation unit exceeds a predetermined threshold, and changes any one or both of a control scheme of the first power supply circuit and the second power supply voltage according to the control signal.