A hydraulic pressure damping device mainly comprises a valve body of which a joint port is provided with a control valve of which one end is provided with a first joint to valve a switch of the valve body between a water inlet and a water outlet. A second joint at the other end of control valve is conjoint with a hydraulic pressure damper to damp the hydraulic pressure. Thus, it is easy to assemble and replace the hydraulic pressure damping device, and materials and installation space may be saved.