This paper proposes a method for reducing the negative spatial harmonics of the radial flux density of an interior-type permanent magnet (IPM) motor. The reliability of the motor is increased by minimizing its vibrations under dynamic eccentricity (DE) state and normal state due to reduction of a negative spatial harmonics component through the influx of a zero spatial harmonics component in the radial flux density. To minimize the vibrations, optimal notches corresponding to the distribution shape of the magnetic field are designed on the rotor pole face. The variations of vibration computation by finite element method (FEM) and the validity of the analysis and rotor shape design are confirmed by vibration and performance experiments.