An object of the present invention is to improve durability of a pressure vessel for blasting an article to be treated such as hazardous substance or explosive therein. The pressure vessel 10, means for achieving the object, has an external vessel 31 and an internal vessel 32 installed in the external vessel 31. The external vessel 31 has a strength for retaining pressure caused by blasting the article. The internal vessel 32 receives fragments of the treated article 100 to protect the external vessel 31 against the fragments. The internal vessel 32 preferably covers almost entire internal surface of the external vessel 31.