To simplify a structure of a pole energizing means and to easily mount the same.

This hydraulic tensioner comprises a piston 3 slidably inserted into a piston hole 2a of a housing 2, defining a fluid chamber 30 with the piston hole 2a, and having rack teeth 3b on a part of its outer periphery, a piston spring 4 for energizing the piston 3 in the projecting direction, a pole member 5 accommodated in a pole hole 2b penetrated through a housing 2 in the direction orthogonal to the piston hole 2a, and having a tooth part 5a engaged with the rack teeth 3b of the piston 3, and a rubber pressure block 6 for pressing the pole member 5 to a side where the tooth part 5a of the pole member 5 is engaged with the rack teeth 3b. By applying the rubber pressure block as the pole energizing means for a pole spring, a structure of the pole energizing means itself can be simplified, and its mounting is also simplified as it can be mounted only by being inserted into the pole hole.