PURPOSE: To recover carbon dioxide gas from waste gas with using low energy by supplying the combustion waste gas to a first gas separation module containing a gas separation membrane to mainly remove water and then supplying the gas not transmitted through the first module to a second gasseparation module.

CONSTITUTION: A large amt. of combustion waste gas discharged from a combustion device of electric power station, etc., is supplied to the first gas separation module 20 containing a gas separation membrane. In this module, water in the combustion waste gas is selectively transmitted and separated from the waste gas, while the waste gas not transmitted through the first separation membrane and containing a considerable amt. of carbon dioxide gas remaining is sent from the first module to the second gas separation module 30. In the second module, carbon dioxide gas is selectively transmitted, while the gas not transmitted through the second module 30, from which water and carbon dioxide gas is sufficiently removed, is discharged to outside of the system. The gas transmitted through the second module 30 and containing high concn. of carbon dioxide gas is recovered from the exit side of the gas separation membrane.