PURPOSE: To provide a gas generator in which a gas flow supply source for forming an aerodynamic window of a gas dynamic laser can be reduced in size.

CONSTITUTION: The gas generator for an aerodynamic window of a laser comprises means for storing gas in a liquid state as a supply source of a gas flow 5 for forming an aerodynamic window 6 of a gas dynamic laser using the window, and means such as a passageway 2 provided in a wall of a burner 1, a nozzle 4, etc., for heat exchanging liquefied gas 3 to the burner 1 of the laser or gas storage to vaporize it to form the flow 5 of the window 6.