A carbon dioxide separation and capture apparatus includes an absorption tower configured to cause an absorbing liquid to absorb a carbon dioxide gas contained in a process gas and a regeneration tower configured to cause the absorbing liquid from the absorption tower to release the carbon dioxide gas. The carbon dioxide separation and capture apparatus further includes an inlet concentration meter configured to measure concentration of an acid component in the process gas supplied to the absorption tower and an outlet concentration meter configured to measure concentration of the acid component in the process gas discharged from the absorption tower. Also included in the carbon dioxide separation and capture apparatus are a supplementary absorbing liquid supply mechanism configured to supply a supplementary absorbing liquid to the main unit and a controller configured to control an amount of the supplementary absorbing liquid supplied to the main unit by the supplementary absorbing liquid supply mechanism based on the concentrations of the acid component measured at the inlet concentration meter and the outlet concentration meter.