A driving support device includes a monitoring unit and an output unit. The monitoring unit monitors whether a sensor to be mounted on a vehicle is operating. The output unit outputs operation-state information indicating a result of the monitoring by the monitoring unit. The monitoring unit detects malfunction of the sensor based on detection accuracy of the sensor. The detection accuracy is received when the sensor operates. The output unit outputs malfunction information on the malfunction of the sensor together with the operation-state information when the monitoring unit detects the malfunction of the sensor.