To provide a power supply control device that supplies electric power to car accessories for various kinds of vehicles during a battery running and an idling stop.

The device includes: a communication unit 34 for communicating with a vehicle-side computer 5 via an in-vehicle communication network 7; a noise detection unit 33 for detecting noise generated from a power supply voltage upon a starting of the vehicle; a relay switch 36 for turning the power supply voltage on/off which is supplied from a power supply to the car accessory 20; and a control unit 35 for using a signal from the vehicle-side computer 5 received by the communication unit 34 and the noise detected by the noise detection unit 33 to control on/off of the relay switch 36.