A stable motor control characteristics can be accomplished by correcting a q-axis current command value by a product of a d-axis current command value (or a detected current value) calculated by field weakening control and a sine signal which is a phase difference between the reference axis of control and the reference axis of the motor. Thereby, a “field weakening vector controller for the permanent magnet synchronous motor” which accomplishes a high-precision, high-response, and high-stability motor torque control even in a field weakening region and which is applicable both to an inexpensive current detecting system and to a system without a pole position detector is provided.