Abstract: A leakage inspecting device for a sealing stopper in a mouth portion of a container, including a positioning member including an inner stand wall, the inner stand wall having a diameter larger than a boundary surface between the mouth portion and a brush attached to the mouth portion and configured to make watertight contact with the mouth portion, a first placing unit configured to place the positioning member on the mouth portion at an inspection spot and align axis centers of the positioning member and mouth portion, a second placing unit configured to place the inner stand wall onto an upper surface of the mouth portion and situate the inner stand wall on the mouth portion, an injection unit configured to inject water into the inner stand wall and mouth portion, and a measuring unit including a probe configured to measure electric conductivity of the water.