Interior permanent magnet synchronous motors (IPMSMs) are used for an electric vehicle (EV) and a hybrid electric vehicle (HEV) due to its high efficiency and high output power density. In particular, the traction motors for the EV and HEV require high efficiency driving in various conditions such as the low load condition and high speed condition. However, it is difficult to change the high efficiency range in the motor, because the magnetomotive force of rotor magnet is constant in conventional IPMSMs. This paper focuses on the leakage flux of the rotor magnet and proposes a variable leakage flux IPMSM (VLF-IPM). The VLF-IPM can change the motor characteristics by simple motor structure drive system because the leakage flux can be controlled by only the armature reaction. This paper shows the principle and the characteristic of VLF-IPM and verifies its effectiveness.