A method of controlling a current by supplying a d-axis current in order to prevent a voltage saturation includes: defining an amount of the d-axis current as Id=|Idmax|·sin θ; continuously comparing a voltage command value with the voltage command value threshold Vo in a predetermined cycle; extracting a predetermined number No of latest comparison results in terms of time; setting a phase angle θ to be 0° when a number N of the comparison results out of the predetermined number No of the comparison results is equal to or less than an integer Nb; and increasing the phase angle θ depending on largeness of the number N when the number N is more than the integer Nb.