In this paper, a new approach is proposed for the optimum design of single-phase induction motor. By using the classical design equations and the evolutionary algorithms such as Genetic Algorithms (GA), Particle Swarm Optimization (PSO) and Modified Particle Swarm Optimization (MPSO), a Single Phase Induction Motor (SPIM) was designed with the maximum efficiency. The Finite Element Method (FEM) was used to achieve an accurate model of the motor. This model was used to validate the optimum design instead of implementing it practically that would be expensive. Results show that the efficiency of the motor designed by MPSO is higher compared to the ones designed by other methods. So this algorithm can be proposed as an appropriate tool in design of single-phase induction motors.