To provide a method and a device for inspecting a liquid container such as a paper cup, used for quantitatively measuring an infinitesimal leak of gas from a liquid container such as a paper cup to determine whether it is not more than an infinitesimal amount of leak not hindering use as a container.

The liquid container 1 such as a paper cup with its mouth part sealed excluding an air inlet port is disposed in a chamber 4 equipped with an air supply port 2 connected to an air supply source 5 and an air exhaust port 3. Air having a prescribed pressure is continuously introduced into the container for a prescribed period of time. Air leaking into the chamber through the wall of the container is introduced into water to form air bubbles 9. The bubbles are detected by a bubble detecting sensor 10 capable of outputting a detection result as an electrical signal. The output of the sensor is processed by a computer 12 to find the quantity of bubbles generated. The quantity of bubbles generated is compared with a prescribed threshold. Whether or not the container is defective is determined depending on whether or not the quantity exceeds the threshold.