Provided is an electronic control device configured to reduce power consumption of a power-supply activation device while maintaining driving of a power supply device. A control unit 18 (the electronic control device) includes an arithmetic device 8, a power supply device 5 which supplies power to the arithmetic device 8, a power-supply activation device 2 which activates the power supply device 5, a power supply maintaining signal line 9 (first signal line), and a reset signal line 11 (second signal line). The power supply maintaining signal line 9 (first signal line) transmits a power supply maintaining signal (power supply drive maintaining signal) for maintaining drive of the power supply device 5, from the arithmetic device 8 to the power supply device 5. The reset signal line 11 (second signal line) transmits a reset signal for resetting the power-supply activation device 2, from the arithmetic device 8 to the power-supply activation device 2.