A rollover determination system 20 includes a first roll rate sensor 22, a lateral G-sensor 26, and a main rollover determination unit 30. The first roll rate sensor 22 detects roll rate of a vehicle. The lateral G-sensor 26 detects acceleration in the lateral direction of the vehicle. The main rollover determination unit 30 determines a possibility of rollover of the vehicle based on roll rate RR and lateral acceleration Gy. A safing determination unit 70 for confirming an occurrence of rollover is additionally incorporated in the main rollover determination unit 30.