IPMSM has been often developed for HEV because it has a high power density and a wide range of operations. However, an armature reaction occurs from the high current and also the hysteresis loss from electrical steel of rotor and stator and the magnet is pretty high due to the high speed driving. Moreover, for IPMSM, there are hardly any accurate specifications or studies to verify the loss through simulative experiment. In this study, the hysteresis loss and eddy current loss are calculated as well as their correlations along with the changes of the current magnitude, current phase angle, and driving speed. In addition, an experiment on loss separation is suggested and its validity is verified through a comparison with the simulation.