A new robust three-dimensional (3-D) shape optimization algorithm is suggested for electromagnetic devices, which combines design sensitivity analysis and adaptive geometric parameterization of the design surface. During the optimization process some extra control points are automatically inserted to describe the shape variations properly, and the control points are maintained so as not to be superfluous but to keep the design surface from oscillating. The newly inserted control points are located around the nodal points which have large fitting sensitivity. Through a numerical application, it is shown that the algorithm ensures a design with good performance as well as a smooth design surface.