In a rollover determining apparatus including a roll rate sensor and a rollover determining unit for determining a rollover of the vehicle on the basis of the roll rate signal to generate a rollover determination signal, which are integrally housed within the vehicle, the rollover determining unit is inhibited from outputting the rollover determination signal when both the collision determination signal and the traveling status determination signal are absent and permitting the rollover determining unit to generate the rollover determination signal when at least one of the collision detection signal indicating a collision of the vehicle and the traveling status detection signal indicating a traveling status of the vehicle is present. The collision may be detected with a front collision sensor and/or a side collision sensor. The traveling status is detected with a vehicle velocity sensor and/or a skid sensor.