PURPOSE: To enable inspection of a drain hole without expending quantities of labors by a method wherein a drain hole is formed in the bottom of an outer box and an inspection window through which the drain hole is seen is formed in the bottom plate of an inner box.
CONSTITUTION: A number of commodities are contained and displayed on a bottom plate 4a. During inspection of a drain hole 21, only commodities on an inspection window 22 is removed once, and the drain hole 21 is inspected through the inspection window 22. When no abnormality occurs to the drain hole 21, a slight amount of the removed commodities are displayed again. When abnormality, e.g. choking of the drain hole 21 with vegetable chips, occurs, commodities on the bottom plate 4a are removed, and a remedy step in which the bottom plate 4a is opened to remove a foreign matter is taken. This constitution prevents expending of a useless labor on inspection of the drain hole 21 and also facilitates an inspection work.