A method of controlling a parallel operation of two inverter power generation apparatuses wherein an unbalance of outputs from the two inverter power generation apparatuses is cancelled by judging that the outputs of the two inverter power generation apparatuses have the collapse of the balance between them when a DC power supply voltage obtained from a DC power supply section exceeds a judgment value set at a value equal to or more than a non-load output voltage of the DC power supply section and allowing an overload operation of the inverter power generation apparatus of higher output voltage among the two inverter power generation apparatuses so as to lower the output voltage of the corresponding inverter power generation apparatus.