PURPOSE: To obtain a high speed gas stream with little turbulence by providing an electrode on the lower source of a high speed gas stream of a gas puff type plasma X-ray source with a hole for taking in a gas stream, while exhausting the inside of a discharge container through it.

CONSTITUTION: A gas puff type plasma X-ray source is formed by a method, in which the inside of a container 6 is exhausted and a high speed gas stream from a nozzle 5 provided on one electrode 2 is formed between the electrodes 1' and 2 while the charge of the capacitor 4 is discharged by closing a switch 3 for taking out a soft X-ray from a window 8. Thereby, a hole 9 for taking the high speed gas stream into the center of the electrode 1' is provided while connecting it to an exhaust pipe 7 in order to exhaust the inside of the container 6 through the hole 9. Accordingly, the air stream from the nozzle 5 is not disturbed by the electrode 1' thus the high speed gas stream having little disturbance being obtainable, while preventing the evaporation material generated by discharge from adhering to the inside wall of the container 6.