To provide a cylinder device capable of enhancing assembling operability.

In the cylinder device including a cylinder 12 in which liquid is encapsulated, an outer cylinder 13 covering the cylinder 12, a rod 15 inserted in the cylinder 12, a rod guide 24 provided at end parts of the cylinder 12 and the outer cylinder 13 and guiding the rod 15 and a seal ring 29 sealing a gap between the rod guide 24 and the outer cylinder 13, the rod guide 24 has a fitted cylindrical surface 52 fitted to the outer cylinder 13, a tapered surface 54 on which the seal ring 29 is disposed together with the outer cylinder 13 and a temporarily holding cylindrical surface 53 having a diameter smaller than that of the fitted cylindrical surface 52 and capable of temporarily holding the seal ring 29 before fitting to the outer cylinder 13.