A power conversion apparatus is disclosed in which AC sides of plural single-phase inverters (IB-INV, 2B-INV, 3B-INV, 2Ba-INV) that convert DC power of DC power sources (V 1B , V 2B , V 3B , V 2Ba ) to AC power are connected in series, and in which gradational output voltage control operation of an output voltage is carried out by using the sum of generated voltages from a predetermined combination selected from the plural single-phase inverters (IB-INV, 2B-INV, 3B-INV, 2Ba-INV). The apparatus is designed such that the plural DC power sources (V 1B , V 2B , V 3B , V 2Ba ) that serve as inputs of the respective single-phase inverters (IB-INV, 2B-INV, 3B-INV, 2Ba-INV) include a first DC power source (V 3B ) having the highest voltage, and another or other plural second DC power sources (V 1B , V 2B , V 2Ba ). Further, the first DC power source (V 3B ) is generated by a third DC power source (2) via a booster circuit (3). Additionally, an output pulse width of the single-phase inverter (3B-INV) that takes the first DC power source (V3 B ) as its input is adjusted so that the total quantity of power fluctuation due to charging and discharging of the respective second DC power sources (V 1B , V 2B , V 2Ba ) via the respective single-phase inverters (IB-INV, 2B-INV, 2Ba-INV) is reduced.