The present disclosure may reduce cogging torque by stacking steel plates which can form a stage skew by stacking the steel plates without reversing the front and back sides or by forming the stage skew by stacking the steel plates capable of easily distinguishing the front and back sides, and reduce both the sixth-order and twelfth-order dq coordinates of harmonic components, thereby achieving low toque ripple, high efficiency, and improved controllability. To this end, the present disclosure is an internal permanent magnet motor having a rotor in which a predetermined skew angle θs is formed between adjacent stages along the axial direction, wherein the rotor is formed by stacking a plurality of the steel plates having the same shape, each of the steel plates has a group of fastening holes made of the same number of the fastening holes as the number of the stages, and each of the fastening holes constituting the fastening group is formed at a position where the skew angle θs changes along a circumferential direction one by one.