Leakage inspection method and leakage inspection device for container to be inspected

A leakage inspection device for a container to be inspected having a deformable flexible portion, the leakage inspection device comprising:

• an inspection chamber which is partitioned from outside and in which the container to be inspected filled with an inspection gas containing helium is disposed;
• a carrier gas supply portion which supplies a carrier gas, of which a concentration of contained helium is different from the concentration of helium contained in the inspection gas, to a lower portion side of the inspection chamber;
• an exhaust portion which exhausts the carrier gas from a position above the container to be inspected in order to form an upward flow of the carrier gas from the lower portion side toward an upper portion side of the inspection chamber;
• and
• a sampling portion which gathers the carrier gas at a position higher than the carrier gas supply portion based on measurement results of a concentration of helium contained in the carrier gas.