This paper presents the robust design of back electromotive force (EMF) characteristic analysis considering the manufacturing tolerances of the permanent magnets (PM) in the interior permanent magnet synchronous motor (IPMSM). We choose the design variables that make an impact on the EMF, and then perform the robust design of EMF using the Taguchi method in order to reduce the effect of variation of the noise variables caused by the manufacturing tolerances. Taguchi method, the most widely known robust design method, is searched for the robust optimum using orthogonal array composed of the product of inner array and outer array. Finally, the robust optimum combination of design variables is selected basis on the result about the manufacturing tolerances of PM. The optimization is verified by comparison of average and variance between robust model and initial model according to the variation of noise factor.