Electric machines for printers require good noise and vibration performance. The polygon mirror scanner motor is an important component of the laser beam printer because it is used to reflect the laser beam of the polygon mirror. Hence, many studies on the improvement of noise and vibration of polygon mirror scanner motor have been carried out. These noise and vibration are classified into electromagnetic, aerodynamic, and structural. Electromagnetic noise and vibration is mainly caused by large cogging torque and non-sinusoidal back EMF. To improve the cogging torque the back EMF of a polygon mirror scanner motor simultaneously, an unequal air-gap model is proposed. To analyze the performance of different models, finite element analysis is applied. To minimize the cogging torque of the proposed model under the limited conditions, the optimal design is performed. As a result of the optimization, the cogging torque and torque ripple were reduced by 47.7% and 23.4%, respectively, while the back EMF and average torque were maintained. The experiment was performed to verify the optimal design results. The experimental results showed that the radial and axial vibration of the optimal model decreased 7.3 times and 3.6 times, respectively, in the 14.2 kHz band.