In a target rotational angle determining routine, based on a roll moment and longitudinal acceleration that are calculated, target rotational angles of actuators on a subject side (one of front-wheel and rear-wheel sides) and a counterpart side are obtained using a common map. An actual rotational angle on the counterpart side is read. It is determined whether the absolute value of a difference obtained by subtracting the actual rotational angle supplied from the counterpart side from the target rotational angle on the counterpart side that is obtained by the subject side is equal to or greater than a set angle difference .DELTA..theta..sub.0. If YES, it is determined that roll stiffness on the counterpart side is insufficient, and the target rotational angle on the subject side is changed so that a roll stiffness distribution ratio between the front-wheel side and the rear-wheel side comes close to a set distribution ratio.