PURPOSE: To aim at improvements in a feeling of driving comfortableness in time of trouble such as disconnection in a signal wire happening, by detecting the consistency or inconsistency between a damping force characteristic indicating signal and a setting state signal being carried out with three stages, and when the inconsistency continues for a specified period, constituting a device so as to stop after rendering the damping force characteristic neutral.

CONSTITUTION: Damping force characteristic indicating signals 22W24 and damping force setting state signals 17a, 17b are all compared with one another by each of inconsistency detecting circuits 18W21 and drive a control circuit 62, a motor drive circuit 63... and so on till they are consistent. On the other hand, such voltage 55 as being increased successively is fed to a flip-flop 51 and an inverter 50 via an alteration detecting circuit 30 or the like, and in time of all circuits being normal, a consistent signal 18... is outputted prior to the stated time T2 whereby a motor comes to a stop as the flip-flop 51 is left unset, but when an inconsistent signal continues to be outputted even after the stated time elapses, the voltage 55 comes high enough, causing the flip-flop 51 to be set, and it outputs a stop signal to a control circuit 12 after neutral position setting. With this constitution, abnormal operation due to trouble is checkable.