In this study, we investigate the demagnetization resistance of a concentrated winding IPMSM (interior permanent magnet synchronous motor) accounting for field weakening control by changing the magnetization direction of the permanent magnet under a high-temperature environment. IPMSMs are investigated by FEA (finite element analysis) using the same volume of the permanent magnet while changing the magnet's width, thickness and magnetic field orientation angle. FEA found that a V-shaped angle Va = 100° and a changed magnet length of 97% using an oblique magnetic-field-oriented magnet strike a good balance between demagnetization resistance and torque at 180 °C. Comparison between demagnetization of negative d-axis current (current phase β = 90°) and demagnetization of field weakening control (β = 80°) using concentrated winding IPMSM with V-shaped angle Va = 100° is conducted. With the demagnetization factor at β = 80° for β = 90°, the demagnetization factor 0.39 (2.6 times) at α = 0° decreases to 0.23 (4.3 times) at α = 20°. The demagnetization resistance in the field weakening control is further improved.