Provided is a compression system including, in order to minimize an amount of oil mixed with a supplied refrigerant, a compressor configured to compress and discharge the refrigerant, a plurality of oil separators configured to separate the oil included in the refrigerant discharged from the compressor, and a refrigerant pipe configured to connect the compressor and the plurality of oil separators to form a travelling path of the refrigerant, and the plurality of oil separators are connected in series along the travelling path of the refrigerant.