A hydraulic tensioner comprises a plunger, and a plunger-accommodating hole in a tensioner housing, together forming a high pressure oil chamber. A plunger-biasing spring is provided in the high pressure oil chamber between the plunger and the bottom of the plunger-accommodating hole. An oil storage chamber is formed inside the plunger, and a check valve unit is press-fit in the rear end of the plunger to allow flow from the oil storage chamber to the high pressure oil chamber while blocking reverse flow of oil.