Removal of CO2 from a simulated biogas consisting of CO2, CH4 and water vapor by pressure swing adsorption (PSA) was experimentally tested for the enrichment of CH4 SAPO-34 and 13X zeolites were employed as adsorbents, of which the former was originally developed for adsorptive desiccant dehumidification. Under the experimental conditions, SAPO-34 adsorbed a smaller amount of CO2 than zeolite 13X, but desorption of adsorbed water vapor from zeolite 13X could not be achieved by vacuum regeneration at room temperature, and thus CO2 separation by PSA zeolite 13X became impossible. In contrast, PSA with SAPO-34 kept its separation performance for the feed gas containing a small amount of water vapor. This allows simplification or omission of pre-drying of the feed gas.