To prevent a vehicle from being unable to revert to its original posture by itself, by preliminary detecting that the vehicle is getting into a state where it is unable to revert to its original posture by itself.

An inclination sensor 18 detects an inclination, and a rolling sensor 20 detects an angular velocity of rolling rotary motion. An ECU 22 determines, based on an inclination and an angular velocity thus detected, whether or not the state of a vehicle 10 after a predetermined period will be one in which it is unable to revert to its original posture by itself. If determining that the vehicle state after the predetermined period will be such a state, the ECU 20 actuates a gas generator 46L so that a suspension 16L on the rolling side is elongated. The gas that the actuated generator 46L produces is supplied to the chamber in the suspension 16L to thus enlarge the chamber or elongate the suspension 16L.