To provide a safe start supporting device to be mounted on a vehicle such as an automobile and allowing the vehicle in the stopped/parked condition to perform a safe start.

On each of the wheels 2 of the vehicle 1, an air pressure sensor unit 31 of a tire air pressure monitoring system is mounted, while a parking brake drum 22 is fitted in each rear wheel 2. Further the vehicle 1 is furnished with an EPB actuator 6 to drive the parking brake drum 22 through a pair of brake cables 5. When an infant etc. carrying a mobile telephone approaches the vehicle 1, the safe start supporting device according to this invention installed in a car-mounted ECU 4 judges the approach from the intensity of the electric wave transmitted from the mobile telephone and emits an engage command to the EPB actuator 6. This puts the brake drum 22 in the engaged condition, and the driver can no more start the vehicle 1.