The irreversible demagnetization of permanent magnets causes the deterioration of the performance in permanent magnet synchronous motors (PMSMs), which are used for electric vehicles. NdFeB, which is the permanent magnet most commonly used in PMSMs for electric vehicles, is easily demagnetized at high temperatures. Because traction motors for electric vehicles reach high temperatures, and a high current can be instantaneously applied, permanent magnets of PMSM can be easily demagnetized. Therefore, it is important to study the demagnetization phenomenon of PMSMs for electric vehicles. However, since the demagnetization analysis procedure is complicated, previous studies have not been able to perform optimization considering demagnetization characteristics. In this study, we optimized the shape of a PMSM for electric vehicles by considering the demagnetization characteristics of permanent magnets using an automated design of experiments procedure. Using this procedure, a finite element analysis for each experimental point determined by a sampling method can be performed quickly and easily. The multi-objective function minimizes the demagnetization rate and maximizes the average torque, and the constraints are the efficiency and torque ripple. Various metamodels were generated for each of the multi-objective functions and constraints, and the metamodels with the best prediction performance were selected. By applying a multi-objective genetic algorithm, 1902 various optimal solutions were obtained. When the weight rate of the demagnetization rate to the torque was set to 0.1:0.9, the demagnetization rate and average torque were improved by 4.45% and 2.7%, respectively, compared to those of the initial model. The proposed multi-objective optimization method can guide the design of PMSMs for electric vehicles with high reliability and strong demagnetization characteristics.