A fluid spring is provided with a sleeve, a first chamber configured to accommodate a fluid and formed in the sleeve, a hollow piston rod, a second chamber configured to accommodate the fluid and formed in the hollow piston rod, and a communicating passage configured to make the first chamber and the second chamber communicate with each other and formed in an end portion of the hollow piston rod. A part of the hollow piston rod is displacably accommodated in the first chamber. The communicating passage only permits the fluid to flow in a direction from the first chamber to the second chamber.