To ventilate by natural ventilation even in an underground type.

The ventilation structure of a spent fuel storage facility is structured by isolating the first underground continuous wall 14a from the building outside wall so that a hollow space 15a is formed between the wall and the first building outside wall 12a, and the hollow space 15a is respectively connected to the air through a ground side opening 16a and to the inside of the spent fuel storage facility through a suction inlet 2. Also, the second underground continuous wall 14b is structured by isolating the wall from the building outside wall so that a hollow space 15a is formed between the wall and the second building outside wall 12b, and the hollow space 15b is respectively connected to the air through a ground side opening 16b and to the inside of the spent fuel storage facility through a exhaust outlet 3.