Proposed is a POD cleaning process including: separating an introduced POD into an inner POD and an outer POD; cleaning a separation POD, which results from the separation, within a cleaning sub-chamber; drying the separation POD, which undergoes the cleaning, within a drying chamber; vacuum-processing the separation POD undergoing the drying; and assembling the inner POD and the outer POD that undergo the vacuum processing, in which the cleaning and the drying are separately performed.