Abstract: Shadow mask in a color cathode ray tube, which provides an appropriate picture quality for a set resolution and has an increased overall strength by a bi-curvatured structure with a reinforced center portion, including a curvature structure formed according to a curvature function g1(x, y), the curvature function g1(x, y) including a peripheral curvature function f1(x, y) of the shadow mask having a predetermined curvature and a central curvature function f2(x, y) having an almost flat curvature, both the predetermined curvature and the almost flat curvature being formed according to an inside surface curvature of a panel, and a curvature function f3(x, y) having a curvature which is stable in view of structure.