A cylinder apparatus includes a base plate, a piston fixed to the base plate and having a piston head and a piston rod connected thereto, a cylinder body having a cylinder chamber defined on one side of the piston head and a cylinder chamber defined on another side of the piston head around the piston rod, the cylinder body being supported for reciprocating movement with respect to the base plate in axial directions of the piston, an upper plate fixed to the cylinder body, and a bushing held in slidable contact with an outer circumferential wall surface of the cylinder body for guiding the reciprocating movement of the cylinder body.