To further improve the protecting function of a piston rod not to give nick and deformation to the piston rod of a cylinder due to collision.

This cylinder protector 20 comprises an exterior protecting pipe 21 and a protecting pipe mounting ring 22, and a guide member 23. The protecting pipe mounting ring 22 is provided on a mounting part 14 connected to the front end of the piston rod 12, and the exterior protecting pipe 21 is connected at one end to the protecting pipe mounting ring 22 and provided extending to the side of a cylinder tube 11. A guide member 23 is mounted on the side of a rod delivery part 16 of the cylinder tube 11 for slidingly guiding the exterior protecting pipe 21. The exterior protecting pipe 21 is long enough to cover the outer face of the guide member 23 even when the hydraulic cylinder 10 is in a most elongating condition. Between the inner face of the exterior protecting pipe 21 and the outer face of the piston rod 12, an almost equal space is formed all over the whole length and periphery.