In an engine type portable generator using an inverter, it sometimes happens that a voltage is developed between the output terminals even when the engine is at rest. A portable generator which inhibits a residual voltage from developing between the output terminals when the engine is at rest and which, after tempovarity converting an ac voltage into a dc voltage, forms a single phase ac voltage and outputs the same, wherein the portable generator includes an output stop controller (443) which, upon the turning-off of an operating switch (305), stops the operation of the inverter circuit in synchronization with the output voltage reduced to zero.