A shock absorber includes first passages configured to communicate two chambers to flow a working fluid therebetween by movement of a piston, and a second passage configured to communicate with one chamber of the two chambers. The first passages have damping valves configured to suppress a flow of the working fluid generated by movement of the piston to generate a damping force. The second passage has a variable orifice having an area adjusted by an elastic member when a piston rod moves in an extension direction, a pressure chamber installed in series with the variable orifice, and a free piston configured to vary a volume of the pressure chamber by movement of the piston.