A gas separation process and a unit therefor. The process comprises the steps of: introducing a gas consisting of two or more components into an adsorption system in which adsorbent particles circulate in a fluidized state, thereby to allow, at atmospheric pressure or an elevated pressure, the adsorbent particles to adsorb a gas component to be separated from the gas; transferring the adsorbent particles adsorbing the gas component to a desorption system; and then desorbing the gas component from the adsorbent particles in the desorption system which is regulated to have either a lower pressure or a lower pressure and a higher temperature than the adsorption system.