Carbon monoxide (CO) is an important platform compound that can be transformed into various fine chemicals. However, CO manufactured by the conventional methods contains many other gases such as hydrogen, methane, nitrogen and carbon dioxide, and additional separation processes are required to utilize CO as a raw material. The current state-of-the-art techniques for separating CO have problems of high energy consumptions. There are needs for an alternate separation process. In this work, we developed a Ni-based adsorbent supported by petroleum-based activated carbon (PAC, BET > 1300 m2/g). The affinity and capacity for CO were evaluated by CO isotherm and CO temperature-programmed desorption. The selectivity to CO was evaluated by the breakthrough test of multicomponent gases (10% H2, 10% CO, 1% CH4, and 1% CO2 with He balance). Ni/PAC was doped with sulfur to increase the CO adsorption activity, and the sulfur-doped Ni/PAC (Ni/PACS) showed outstanding CO adsorption capacity, which is 9 times higher than that of the sulfur-free Ni/carbon adsorbent (Ni/PAC). The Ni/PACS could recover the CO to over 99% purity from the multicomponent gases. The sulfur-doped Ni/carbon adsorbent showed high affinity, high capacity, and high selectivity for CO separation.