A strut assembly forming an upper part of a cylinder joined to a wheel is joined to a vehicle body via an insulator and joining member, an airtight chamber space is formed by a strut cover joined to a spring body joined to a damper rod drawn from the cylinder, whereby a CDC type damper with the chamber space of which air pressure is controlled in order to vary the movement characteristic depending on movement of a tire and a damper joined to an inner space of the spring body has an urethane made damper guider having dug air channels where air moves even in a state where the damper is in close contact with the damper rod.