Abstract: A portable generator in whose casing are housed an engine and a generator directly connected to and driven by the engine. A single cooling fan is provided at the connecting portion of a crankshaft in said engine and a revolving shaft in said generator to produce a unidirectional cooling air flowing from the generator side through the outside and inside of the generator to the engine side, as well as air intake and exit ports are provided in said casing side walls respectively in the vicinity of the side surface opposite to the engine of said generator and opposite to the generator of said engine, thus resulting in a high cooling efficiency of and an enhanced soundproof effect on the engine and generator as well as in a more compact generating system.