An apparatus for detecting a rollover of a vehicle is provided. The apparatus comprises a detector, memory unit, calculator, and rollover determination unit. The detector detects a roll angular velocity of the vehicle. The memory unit memorizes a value of the roll angular velocity detected by the detector. The calculator calculates a predictive value to the roll angular velocity to be expected when a predetermined period of time elapses, by using a past value of the roll angular velocity of the vehicle, the past value being memorized in the memory unit. The rollover determination unit determines whether or not there is a possibility that the vehicle will make a rollover, on the basis of the predictive value to the roll angular velocity.