A shock absorber includes a cylinder tube, a piston fitted slidably in an axial direction in the cylinder tube and arranged to divide an inside of the cylinder tube into first and second fluid chambers, a piston rod extending from the piston to an outside of the cylinder tube, and damping force generation sections arranged to generate a damping force by making hydraulic fluid flow between the first and the second fluid chambers. Cavities are formed in at least one of the cylinder tube and the piston rod. Flowable matter having a rheological characteristic is sealed in the cavities.