PROBLEM TO BE SOLVED: To provide a method for producing carbon dioxide, an apparatus for producing carbon dioxide, and a system for producing carbon dioxide which enable separation of high-purity (a purity of 90% or more) methane and high-purity (a purity of 99% or more) carbon dioxide from a biogas.SOLUTION: The method for producing carbon dioxide comprises: performing an adsorption step, a purging step, and an exhaust recovering step with phases shifted by using three adsorption towers; completing the exhaust recovering step when an amount of carbon dioxide adsorbed by adsorbent reaches a saturated state; and making time for performing separation of methane equal to or longer than time for performing a step of purging carbon dioxide.
