Hydraulic tensioner of the present invention comprises housing having piston bore that extends in the axial direction and opens at one end; hollow piston fitted in the piston bore of the housing to slide in the axial direction, and has stepped shoulder portion in a position rearward of one end to apply tension to the chain; piston spring for biasing the piston in the protruding direction by the force resulting from the hydraulic pressure inside the hollow interior; means for restricting retraction, which can restrict the retraction of the piston within a predetermined range retaining pin for retaining the means for restricting retraction; and retaining means releasably engaged near the piston to limit the protruding range of the flange within a predetermined range at the time of releasing the retaining pin.
