A rollover judging device adjusts the magnitude of an angular velocity component ω of a vehicle in a direction of a rollover, which is measured by an angular velocity sensor 1, by using an ω adjusting unit 3c on the basis of an acceleration component of the vehicle in its rightward or leftward direction or in its upward or downward direction, which is measured by an acceleration sensor 2, calculates an angle component θo by integrating with respect to time this adjusted angular velocity component ωo by using an integrator 3d, carries out predetermined multiplication and addition processes by using a judging means 4 on the basis of this angle component θo and the measured angular velocity component ω, and, when the result of this addition process exceeds a preset threshold Th, outputs a signal indicating judgment of occurrence of a rollover to an air bag control device 5.