A cylinder device includes a cylinder, an outer tube, a piston, a piston rod, a rod guide, a first common passage through which working oil that is supplied/discharged to/from a rod-side chamber passes, a pipe that forms a part of the first common passage and is provided in a reservoir tank, a pipe holder that is provided between the pipe and the rod guide and holds a first end of the pipe, and a plug that is provided on a side of the pipe holder opposite from the pipe and has a throttle passage allowing the first common passage to communicate with the reservoir tank.