<p>Disclosed is a lash adjuster in which a return spring can be prevented from being excessively compressed when an adjust screw is pressed into a nut member and form-rolling of a male screw on the outer periphery of the adjust screw is easy. A lash adjuster (1) comprises an adjust screw (15) having a male thread (14) engaged with a female thread (13) of a nut member (12) on the outer periphery thereof and a return spring (17) biasing the adjust screw (15) in a direction in which the adjust screw projects from the nut member (12), and swingably supports an arm (7) of a valve operating device at the projecting end of the adjust screw (15) from the nut member (12). The movement of the adjust screw (15) in a direction in which the adjust screw is pressed into the nut member (12) is restricted by providing a stopper (23) with a diameter larger than the internal diameter of the nub member (12) in a projecting portion of the adjust screw (15) from the nut member (12) and stopping the stopper (23) at the open end of the nut member (12).</p>
