PURPOSE: To judge the degree of sealing and capacity change of an empty container, by applying a positive or a negative differential pressure between the inner pressure of the empty container and the pressure within a test room to the empty container in the test room and using the pressure state in the test room. CONSTITUTION: A hollow container 1 is loaded into a test room 3. An inner pressure Pi1 corresponding to a normal surrounding pressure Pu is applied to the inside of the hollow container 1. After the test room 3 is airtightly sealed, a pressure is applied to the test room 3 while being connected to a pressure medium liquid 7, thus generating a positive or a negative differential pressure corresponding to the inner pressure Pi1 in the hollow container 1 within the test room 3. Then, a pressure system consisting of the test room 3 and the hollow container 1 is shut off from a pressure medium source by a shielding valve 9 and is left. When the hollow container 1 is airtight and the wall is stiff so that no remarkable deformation occurs in the wall due to force generated by the differential pressure between P1 and Pi1 , an output signal S (P3 ) is recorded by a pressure detector 11.