When there is a restriction in an outfitting space, a mounted engine generator unit requires an operation restriction such as, for example, the current restriction of a generator if a sufficient heat capacity is not ensured. Therefore, this drive control device is provided with: a power conversion circuit for converting the AC power generated by the generator driven by an engine to a DC power; and a control unit for controlling the switching operation of the power conversion circuit on the basis of a switching operation mode. The control unit changes the switching operation mode in accordance with the rotational speed of the generator driven by the engine, thereby reducing and furthermore minimizing the percentage of the harmonic components of AC current for driving the generator.