A cylinder device comprising: a cylinder; a piston slidably inserted into the cylinder thereby to divide an interior of the cylinder into a rod-side chamber and a piston-side chamber; a piston rod having an end coupled to the piston; an external cylinder disposed outside the cylinder and covering the cylinder; a tank formed in a space between the cylinder and the external cylinder and storing an operating fluid; piping (30, 40, 50) constituting part of a passage (T1, T2, T8) through which the operating fluid passes when the operating fluid is supplied into and discharged from the rod-side chamber or the piston-side chamber, the piping (30, 40, 50) being disposed in the tank; a cover member (12, 112, 212) closing one end of the cylinder and one end of the external cylinder and formed with a first communication hole which is open to an interior of the tank and into which one end of the piping (30, 40, 50) is inserted; a rod guide (20, 120, 220) which closes the other end of the external cylinder and the other end of the cylinder and into which the piston rod is movably inserted; and a flow passage forming member provided between the cylinder and the external cylinder and coupled to the rod guide (20, 120, 220), the flow passage forming member being formed with a second communication hole which is open to the interior of the tank and into which the other end of the piping (30, 40, 50) is inserted, characterized in that: the piping has a piping body and insertion members (32, 33) respectively coupled to both ends of the piping body; the piping has a length shorter than a distance between an inner end surface of the first communication hole and an inner end surface of the second communication hole; and the insertion member coupled to one end of the piping body has a larger outer diameter than the insertion member coupled to the other end of the piping body. a cylinder; a piston slidably inserted into the cylinder thereby to divide an interior of the cylinder into a rod-side chamber and a piston-side chamber; a piston rod having an end coupled to the piston; an external cylinder disposed outside the cylinder and covering the cylinder; a tank formed in a space between the cylinder and the external cylinder and storing an operating fluid; piping (30, 40, 50) constituting part of a passage (T1, T2, T8) through which the operating fluid passes when the operating fluid is supplied into and discharged from the rod-side chamber or the piston-side chamber, the piping (30, 40, 50) being disposed in the tank; a cover member (12, 112, 212) closing one end of the cylinder and one end of the external cylinder and formed with a first communication hole which is open to an interior of the tank and into which one end of the piping (30, 40, 50) is inserted; a rod guide (20, 120, 220) which closes the other end of the external cylinder and the other end of the cylinder and into which the piston rod is movably inserted; and a flow passage forming member provided between the cylinder and the external cylinder and coupled to the rod guide (20, 120, 220), the flow passage forming member being formed with a second communication hole which is open to the interior of the tank and into which the other end of the piping (30, 40, 50) is inserted, characterized in that: the piping has a piping body and insertion members (32, 33) respectively coupled to both ends of the piping body; the piping has a length shorter than a distance between an inner end surface of the first communication hole and an inner end surface of the second communication hole; and the insertion member coupled to one end of the piping body has a larger outer diameter than the insertion member coupled to the other end of the piping body. the piping has a piping body and insertion members (32, 33) respectively coupled to both ends of the piping body; the piping has a length shorter than a distance between an inner end surface of the first communication hole and an inner end surface of the second communication hole; and the insertion member coupled to one end of the piping body has a larger outer diameter than the insertion member coupled to the other end of the piping body.