A low cost hydraulic tensioner of die-casting metal or synthetic resin with a separate metallic cylinder free from dropping out of the cylinder and fine surface finishing, is provided. The tensioner 1 comprises a metallic cylinder 4 fitted to a cylindrical hole 3 formed in a body 2, a plunger 5 energized by a spring 7 and a pressure oil chamber 8 formed between the inner part of plunger 5 and the cylinder 4. The cylinder 4 is provided with a bottom plate 4B having a through hole 4A allowing the inflow of oil. The bottom plate 4B is prevented from dropping out from the body 2 by being engaged by the spring 7.