ELECTRONIC CONTROL DEVICE

Provided is an electronic control device capable of performing abnormality diagnosis of a digital input circuit without modifying the circuit configuration. Included are: an external connection terminal to which an external power supply is connected; a first capacitor having one end connected to the external connection terminal and the other end connected to circuit ground; a microcomputer having a D/I port which is an input/output port and to which a voltage of the external connection terminal is input; an RC filter provided between the D/I port and the first capacitor, the RC filter including a first resistor and a second capacitor; and a second resistor for dividing an output voltage of the D/I port together with the first resistor and applying the divided voltage to one end of the first capacitor, in which the microcomputer outputs a predetermined voltage from the D/I port and diagnoses a connection condition of the external connection terminal on the basis of a voltage input to the D/I port after the first capacitor is charged with the predetermined voltage.