Abstarct: In the conventional design of electrical machines, the overall geometry is predefined and the designer determines appropriate dimensions baxsed on the overall geometry, while this geometry itself may not be optimal. In the proposed method, there is no assumption for geometry and it is formed during optimization design. This method is applied to the rotor of a switched reluctance motor (SRM) with four poles on the stator and two poles on the rotor. The rotor boundary is defined by a few B-splines. The B-splines have been used to design machines and electromagnetic devices. However, this method is used for the first time in design of the whole rotor of an SRM. Some control points are located around the rotor and changing their locations causes customized changes in the rotor boundary. Locations of these points are defined as design variables. A 2-D finite element analysis using MATLAB/PDE is applied to the SRM model and an optimization algorithm is employed to design procedure by means of achieving the best likeness between desired and computed static torques. The results of the analysis show that the proposed method has a much greater capability to match different objective functions. For the proposed objective function, the torque profile of the motor designed with a B-spline rotor differs by about 17% from the desired torque, while this difference reaches 40% for the motor designed with a conventional geometry. Experimental results from a prototype motor have a close agreement with analysis results.