A variable-curvature mirror for a laser which makes it possible to obtain a high-accuracy spherical surface by uniformly deforming a reflecting mirror under a low load without stroke loss of an actuator. A top lid has a restricting surface for receiving the peripheral portion of the reflecting mirror to prevent translational movement of the reflecting mirror in the pressurizing direction. A gap is formed to permit pivotal motion of the peripheral portion of the reflecting mirror about the contact point with the top lid. Its thickness is radially changed so that its thickness reduces toward the peripheral portion. The reflecting mirror can thus be smoothly and uniformly deformed.
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