To provide an external combustion engine generator which is driven by combustion gas of relatively low temperature by biomass fuel with a simple structure and has excellent heat efficiency.

The external combustion engine generator is provided with: an external engine driven by using volumetric expansion by heat-expanding compressed air by heating; an air compressor constituted of a casing and a turbine housed therein; an air heating unit heating and expanding air supplied from the air compressor; a rotary driving unit constituted of the casing and turbine housed therein and using the heated expanded air flowing from the air heating unit as an energy source; and a heat source used for heating air at the air heating unit. Rotary shafts of the air compressor and rotary driving unit are coaxially formed, and a generation electric motor is provided to the rotary shaft end of the compressor side to start an engine by the generation electric motor when starting the engine, to generate power by the generation electric motor after driving the external combustion engine.