To inhibit the performance deterioration of a porous membrane due to the clogging of its pores with included solid particles, when the gas of an absorbing liquid is dissipated into a vacuum space by injecting the absorbing liquid into the vacuum space through micropores of the porous membrane.

A gas to be separated and the absorbing liquid are brought into gas-liquid contact with each other through a gas permeable membrane. Through this process, the absorption of a specific component gas of the gas to be separated by the absorbing liquid can be achieved without including the solid particle in the gas to be separated into the absorbing liquid. Following this procedure, the absorbing liquid which has absorbed the specific component gas is brought into contact with the more pressure-reduced space than the absorbing liquid side through the liquid permeable porous membrane, and the absorbing liquid is jetted into the vacuum space through the fine pores of the porous membrane. Thus the specific component gas contained in the absorbing liquid is dissipated into the vacuum space to achieve the separation of the specific component gas.