A method of automatically tuning a power conversion apparatus that drives an induction motor, the method comprising: in an auto tuning mode, a step in which a V/f control unit (5, 5') that outputs a voltage command value of the induction motor changes a ratio of an output voltage of the induction motor to an output frequency of the induction motor to change a voltage command value over several stages; and a step in which a current detection means detects an excitation current that changes in several stages; characterized in that the method further comprises, in the auto tuning mode: a step in which a mutual inductance calculation unit calculates reactive power on the basis of the voltage command value, a current detection value, and a speed command value and estimates, from the reactive power, a mutual inductance of the induction motor that changes in several stages; and wherein the method further comprises: in a vector control mode, a step in which a magnetic flux axis current/magnetic flux command setting unit outputs a current command value and a secondary magnetic flux command value on the basis of a mutual inductance value and an excitation current value measured in the auto tuning mode; and a step in which a vector control calculation unit outputs a voltage command value of the induction motor on the basis of the current command value and the secondary magnetic flux command value, wherein in the step of outputting the current command value and the secondary magnetic flux command value, the magnetic flux axis current/magnetic flux command setting unit sets a mutual inductance value in a saturated state and an excitation current value at that time in a low speed range and sets a mutual inductance value in a normal state and an excitation current value at that time in a middle and high speed range. in an auto tuning mode, a step in which a V/f control unit (5, 5') that outputs a voltage command value of the induction motor changes a ratio of an output voltage of the induction motor to an output frequency of the induction motor to change a voltage command value over several stages; and a step in which a current detection means detects an excitation current that changes in several stages; characterized in that the method further comprises, a step in which a mutual inductance calculation unit calculates reactive power on the basis of the voltage command value, a current detection value, and a speed command value and estimates, from the reactive power, a mutual inductance of the induction motor that changes in several stages; and wherein the method further comprises: in a vector control mode, a step in which a magnetic flux axis current/magnetic flux command setting unit outputs a current command value and a secondary magnetic flux command value on the basis of a mutual inductance value and an excitation current value measured in the auto tuning mode; and a step in which a vector control calculation unit outputs a voltage command value of the induction motor on the basis of the current command value and the secondary magnetic flux command value, in a vector control mode, a step in which a magnetic flux axis current/magnetic flux command setting unit outputs a current command value and a secondary magnetic flux command value on the basis of a mutual inductance value and an excitation current value measured in the auto tuning mode; and a step in which a vector control calculation unit outputs a voltage command value of the induction motor on the basis of the current command value and the secondary magnetic flux command value, wherein in the step of outputting the current command value and the secondary magnetic flux command value, the magnetic flux axis current/magnetic flux command setting unit sets a mutual inductance value in a saturated state and an excitation current value at that time in a low speed range and sets a mutual inductance value in a normal state and an excitation current value at that time in a middle and high speed range.