Abstract: A hydraulic damping device has a cylinder, a rod, a piston, a first biasing member, a seal and a second biasing member. The rod moveably extends into the cylinder. The piston is securely attached to the rod to divide the cylinder into two chambers. The piston has multiple first channels and multiple second channels communicating with the chambers, wherein each first channel has a diameter larger than that of each second channel. The first biasing member is connected to the rod to provide a recoil force to the rod. The seal is moveably mounted on the rod and abuts against the piston to close the first channels in the piston. The second biasing member is mounted on the rod to provide a force to push the seal. Accordingly, the hydraulic damping device has a capability of adjusting the damping effect and has a simplified structure.