An inverter power generator (1, 1A, 1B) comprising: an engine; an actuator for adjusting a position of a throttle valve of the engine; a power generating unit for generating AC power from a driving force of the engine; a converter for converting the AC power outputted from the power generating unit into DC power; an inverter for converting the DC power outputted from the converter into AC power; a current detection unit for detecting a current of the AC power outputted from the inverter; a voltage detection unit for detecting a voltage of the AC power outputted from the inverter; a target rotation speed determination unit for determining a target rotation speed of the engine, based on a detected current value detected by the current detection unit and a correction value (k) in accordance with a difference between a target voltage value of the AC power outputted from the inverter and a detected voltage value detected by the voltage detection unit; and an actuator control unit for controlling the actuator based on the target rotation speed determined, characterised in that the target rotation speed determination unit is configured to determine the target rotation speed, based on a power value and the correction value (k), the power value being calculated, based on the detected current value and the detected voltage value, wherein the target rotation speed determination unit is configured to determine the target rotation speed, based on a corrected power value calculated based on the power value and the correction value (k), and wherein the corrected power value is a value obtained by dividing the power value by a ratio of the detected voltage value to the target voltage value. an engine; an actuator for adjusting a position of a throttle valve of the engine; a power generating unit for generating AC power from a driving force of the engine; a converter for converting the AC power outputted from the power generating unit into DC power; an inverter for converting the DC power outputted from the converter into AC power; a current detection unit for detecting a current of the AC power outputted from the inverter; a voltage detection unit for detecting a voltage of the AC power outputted from the inverter; a target rotation speed determination unit for determining a target rotation speed of the engine, based on a detected current value detected by the current detection unit and a correction value (k) in accordance with a difference between a target voltage value of the AC power outputted from the inverter and a detected voltage value detected by the voltage detection unit; and an actuator control unit for controlling the actuator based on the target rotation speed determined, characterised in that the target rotation speed determination unit is configured to determine the target rotation speed, based on a power value and the correction value (k), the power value being calculated, based on the detected current value and the detected voltage value, wherein the target rotation speed determination unit is configured to determine the target rotation speed, based on a corrected power value calculated based on the power value and the correction value (k), and wherein the corrected power value is a value obtained by dividing the power value by a ratio of the detected voltage value to the target voltage value.