A chain tensioner includes a cylinder having a closed end, an internally threaded plunger axially slidable in the cylinder, a return spring biasing the plunger in the protruding direction from the cylinder, and a screw rod having an external thread in threaded engagement with the internal thread of the plunger. The portion of the screw rod protruding from the plunger abuts a rod seat provided in the cylinder. The screw rod has a rolled external thread and an intermediate portion protruding from the plunger and having an outer diameter smaller than the diameter of the root of the external thread. The screw rod has a forged contact surface, to be contacted with the rod seat, on the axial end face of the intermediate portion. The internal thread may be formed by pressing, and a pressed recess, corresponding to the internal thread, may be formed on the plunger's outer circumference.