To restrain a heat pull to a knuckle from a damper rod, and to improve heating efficiency of a pressure medium by a heat source by interposing a heat insulating member between the damper rod vertically movably inserted into a damper main body from below and a cylindrical case connected to this damper rod.

When a case 8 is directly connected to a damper rod 2, the damper rod 2 and a knuckle N are thermally connected through the case 8 and a bracket 12. Here, since the knuckle N has large heat capacity and functions as a heat sink part, a heat pull to the knuckle N from the damper rod 2 is caused, so that even if a heat insulating layer 8c is arranged, heating efficiency of a pressure medium by an electric heater 10 is not improved. Then, the damper rod 2 and the case 8 are connected through a heat insulating member 17 such as a urethane resin and rubber. Heat conduction between the damper rod 2 and the case 8 is cut off by the heat insulating member 17 to restrain the heat pull to improve heating efficiency of the pressure medium by the electric heater 10.