PURPOSE: To prevent accidents by generating different alarms respectively when a vehicle retreats along a slope during parking even if parking brake is operated or when the vehicle starts as the parking brake is applied.

CONSTITUTION: When a vehicle is parking on a slope and retreats even if parking brake is applied, a vehicle speed sensor 1 generates the detecting signal which is compared with reference voltage V1 through F/V converter 2 by a comparator 3. When said detecting signal voltage exceeds V1, the comparator 3 generates the H signal to AND circuit 11. Since a parking brake switch 5 is turned on, the AND circuit 11 generates the H signal to a buzzer controlling circuit 12. Also, as an engine is in idling, the signal of low level from a rotational frequency sensor 8 is sent to the input of the buzzer controlling circuit 12 which operates continuously a buzzer 13. When the vehicle starts and travels as the parking brake is applied, the control circuit 12 operates intermittently the buzzer 13 with HV level signal of the sensor 8.