A rigid pressure container for disposing of an object to be treated by blasting operation performed therein, said pressure container comprising: a sealable outer vessel constituting an outer shell of said pressure container, said sealable outer vessel being formed of steel; and an inner vessel disposed inside said outer vessel for receiving an impact load produced at the time of blasting operation, said inner vessel being formed of steel; wherein said inner vessel has a pressure relieving part which can discharge part of high-pressure gas produced in said inner vessel at the time of blasting operation into a gap between said inner vessel and said outer vessel; wherein said outer vessel has a shape extending in a specific direction and includes a main outer vessel body having at one of two ends thereof an outer opening (31 a) and an outer lid for opening and closing the outer opening (31 a), and said inner vessel has a shape extending in a specific direction and includes a main inner vessel body having at one of two ends thereof an inner opening (41 a) and an inner lid provided on a side corresponding to the outer lid for opening and closing the inner opening (41 a); wherein the main inner vessel body and the inner lid are separated from each other so that a gap is formed between the main inner vessel body and the inner lid, and part of the high-pressure gas is discharged into the gap between said inner vessel and said outer vessel through the gap which is formed between the main inner vessel body and the inner lid and serves as the pressure relieving part; and wherein the inner lid is mounted in such a manner that the inner lid can be displaced relative to the main inner vessel body, whereby the gap between the main inner vessel body and the inner lid automatically spreads out according to the magnitude of the impact load. a sealable outer vessel constituting an outer shell of said pressure container, said sealable outer vessel being formed of steel; and an inner vessel disposed inside said outer vessel for receiving an impact load produced at the time of blasting operation, said inner vessel being formed of steel; wherein said inner vessel has a pressure relieving part which can discharge part of high-pressure gas produced in said inner vessel at the time of blasting operation into a gap between said inner vessel and said outer vessel; wherein said outer vessel has a shape extending in a specific direction and includes a main outer vessel body having at one of two ends thereof an outer opening (31 a) and an outer lid for opening and closing the outer opening (31 a), and said inner vessel has a shape extending in a specific direction and includes a main inner vessel body having at one of two ends thereof an inner opening (41 a) and an inner lid provided on a side corresponding to the outer lid for opening and closing the inner opening (41 a); wherein the main inner vessel body and the inner lid are separated from each other so that a gap is formed between the main inner vessel body and the inner lid, and part of the high-pressure gas is discharged into the gap between said inner vessel and said outer vessel through the gap which is formed between the main inner vessel body and the inner lid and serves as the pressure relieving part; and wherein the inner lid is mounted in such a manner that the inner lid can be displaced relative to the main inner vessel body, whereby the gap between the main inner vessel body and the inner lid automatically spreads out according to the magnitude of the impact load.