A multilevel inverter having a cascade configuration for supplying a device for equally controlling a power factor of each unit cell, of a plurality of power cells (4-1,..., 4-n), the inverter comprising: a master controller configured to generate and output a control output from an output voltage and an output frequency according to a set control command; the plurality of power cells (4-1,... 4-n) connected in series with respect to each phase, each power cell including an AC-DC converter for converting a three-phase AC input voltage into a DC output voltage according to the control output from the master controller, a smoothing circuit for smoothing the converted DC voltage from the AC-DC converter, and an inverter for generating an AC output voltage using the smoothed DC voltage as an input voltage; a phase shift transformer for supplying a power cell input voltage, the transformer having a primary winding connected to a three-phase AC power source, and a plurality of secondary windings correspondingly connected to each of the plurality of power cells; a communication network connected between the master controller and each of the plurality of power cells to provide a communication path therebetween; cell controllers (3-1,..., 3-n) connected to each of the plurality of power cells and the master controller and configured to control output voltages and output frequencies of each of the connected plurality of power cells according to a voltage command and a frequency command from the master controller, each cell controller comprising a pulse width modulator for generating a chopping wave as a reference for a pulse width modulation so as to generate a pulse width modulation control signal of a variable voltage and variable frequency, and provide the generated pulse width modulation control signal to the respective connected power cell, wherein each cell controller is configured to calculate a phase difference value of the respective connected power cell according to a preset total number of the plurality of power cells connected to a single phase and a floor number of the respective connected power cell so that each of the plurality of power cells has the same power factor, and to phase-shift the chopping wave by the calculated phase difference value, to compensate for phase differences between each of the plurality of power cells, characterized in that the cell controller is configured to calculate the phase difference value by a calculation formula, wherein the phase difference value = 180 ° / 2 n + 180 ° / n × the floor number of the corresponding power cell -1, where n denotes the total number of power cells for a single phase. a master controller configured to generate and output a control output from an output voltage and an output frequency according to a set control command; the plurality of power cells (4-1,... 4-n) connected in series with respect to each phase, each power cell including an AC-DC converter for converting a three-phase AC input voltage into a DC output voltage according to the control output from the master controller, a smoothing circuit for smoothing the converted DC voltage from the AC-DC converter, and an inverter for generating an AC output voltage using the smoothed DC voltage as an input voltage; a phase shift transformer for supplying a power cell input voltage, the transformer having a primary winding connected to a three-phase AC power source, and a plurality of secondary windings correspondingly connected to each of the plurality of power cells; a communication network connected between the master controller and each of the plurality of power cells to provide a communication path therebetween; cell controllers (3-1,..., 3-n) connected to each of the plurality of power cells and the master controller and configured to control output voltages and output frequencies of each of the connected plurality of power cells according to a voltage command and a frequency command from the master controller, each cell controller comprising a pulse width modulator for generating a chopping wave as a reference for a pulse width modulation so as to generate a pulse width modulation control signal of a variable voltage and variable frequency, and provide the generated pulse width modulation control signal to the respective connected power cell, wherein each cell controller is configured to calculate a phase difference value of the respective connected power cell according to a preset total number of the plurality of power cells connected to a single phase and a floor number of the respective connected power cell so that each of the plurality of power cells has the same power factor, and to phase-shift the chopping wave by the calculated phase difference value, to compensate for phase differences between each of the plurality of power cells, characterized in that the cell controller is configured to calculate the phase difference value by a calculation formula, wherein the phase difference value = 180 ° / 2 n + 180 ° / n × the floor number of the corresponding power cell -1, where n denotes the total number of power cells for a single phase.