A CO2 separation system configured to separate CO2 from mixed gas containing CO2 includes a CO2 separator, a CO2 collector, and a pressure difference generator. The CO2 separator includes a separation membrane configured to separate the CO2 from the mixed gas, and a separation-membrane upstream chamber and a separation-membrane downstream chamber demarcated by the separation membrane. The CO2 separator is disposed to cause the mixed gas to flow into the separation-membrane upstream chamber. The pressure difference generator includes at least a negative pressure generator. The negative pressure generator is disposed on a gas path of the permeating gas that connects the separation-membrane downstream chamber and the CO2 collector.