Output control device for hybrid engine-driven power generator

An alternator output can be assisted by a battery output even when a battery voltage is lower than an output voltage of an alternator. A power generator (1) has a battery (4) and an alternator (3) driven by an engine (2). The battery (4) assists a power energy of the alternator (3). An inverter circuit (52) is connected to an output of a rectifying circuit (51). A DC/DC converter (9) boosts a voltage of the battery (4) and inputs the boosted voltage into a constant power regulator (21). The constant power regulator (21) boosts an input voltage and secures a certain power. An output voltage of the rectifying circuit (51) is monitored by a monitoring means (30a) and an output voltage of the battery (4) is monitored by a monitoring means (29a). When the output voltage of the rectifying circuit (51) is equal to or less than a rated voltage, an auxiliary power value corresponding to the remaining amount of the battery is set as a power target value of the constant power regulator (21).