Provided is a tensioner which can ensure, with a simple structure, both the stability of the installation state of a check valve and the capacity of an oil storage chamber. A tensioner has a plunger, a housing, a check valve, and a coil spring. The plunger has a front-side plunger part having a pressing front end portion, and a rear-side plunger part disposed on the rear side of the front-side plunger part and having a valve movement restricting portion. The check valve is disposed on the rear side of the valve movement restricting portion. The coil spring is disposed so that one end thereof is in contact with a housing bottom portion and the other end thereof is in contact with the rear side of the check valve.