PURPOSE: To provide a method to separate and recover carbon monoxide gas from mixture gas at a high yield with a low cost for facilities.

CONSTITUTION: Carbon monoxide is separated and recovered by using a pressure swing adsorption method. In this method, the pressure in the adsorption tower after the adsorption process is completed is released under such conditions that the pressure is lower than the partial pressure of carbon monoxide in the source material, the amt. of gas released is under 50% of the gas amt. adsorpted, and the pressure after release is the same or higher than atmospheric pressure. Thus, impurities remaining in the tower is purged out with the gas through the exit of the adsorption column. After releasing pressure, the product gas is partly introduced to the tower to completely remove impurities in the tower. The gas perged with the product gas is introduced to another adsorption column to increase the pressure in the adsorption tower while carbon monoxide in the purged gas is adsorbed in this adsorption column. After completing purging, the column is evacuated into vacuum to recover carbon monoxide adsorbed to the adsorbent.