A micro turbine generator includes a compressor, a guide channel, an expansion chamber, and a recuperator. The expansion chamber includes an air inlet, an air outlet, and a guide vane structure. The air inlet is disposed at one end of the expansion chamber, connected with the compressor through the guide channel, and receives an air compressed by the compressor. The air outlet is disposed at the other end of the expansion chamber, connected with the recuperator, and discharges the air, allowing the air to enter the recuperator. The guide vane structure extends inward from an inner wall of the expansion chamber to allow the air to pass the guide vane structure before being discharged from the air outlet to enter the recuperator.