To provide a method and a device for inspecting poor sealing of a container capable of inspecting a pinhole without being influenced by an initial strain of the container.

A container 12 having multi-layered films 26 adhered thereto and having a straw 28 protruded out of their adhering surfaces is inserted into a container holding segment 16 having a clearance 50 for restricting a degree of expansion so as to perform a pressurization of the container 12 and releasing of the container through the straw 28. Then, after completion of the aforesaid work, pressurization of the container 12 is carried out and then a presence or a non-presence of pin hole of the container 12 is discriminated in reference to an amount of reduction of pressure varied as time elapses.