A non-destructive inspection device for an oxygen concentration in a bag-shaped container includes: right and left affixing plates provided so as to be moved toward and away from the bag-shaped container; a laser emitting section for measuring an oxygen concentration that is provided on one of the affixing plates; and a laser receiving section on the other affixing plate, wherein the end faces of the emitting section and the receiving section have gas-filled chambers that include gas chambers with a constant length and are made of a translucent material. In the measurement of an oxygen concentration, the affixing plates are brought close to each other, the thickness of a gas phase portion is kept constant, and air is removed between the end faces of the emitting section and the receiving section and the surfaces of the container.