Phase voltage setting means defines an actual current phase region including a current phase error range based on parameters including an individual difference of at least any one of a motor and an inverter, defines a stable operation current phase region in which a rotor position can be detected through sensorless control, and sets, as a target current, an electric current obtained by adding a predetermined phase difference corresponding to the number of revolutions detected by revolution number detecting means to an electric current set by current vector control such that the actual current phase region is within the stable operation current phase region.