A CA system includes a gas supply device which performs a gas supply operation of supplying nitrogen-enriched air into a container, and a controller which performs the gas supply operation so that the inside air has a desired composition. The controller performs carbon dioxide priority control in which the controller performs the gas supply operation if an oxygen concentration of the inside air is equal to or higher than a ceiling concentration higher than a target oxygen concentration, stops the gas supply operation if a carbon dioxide concentration of the inside air is lowered to a critical concentration lower than a target carbon dioxide concentration, and restarts the gas supply operation if the carbon dioxide concentration of the inside air has reached a restart concentration higher than the target carbon dioxide concentration through breathing of the plants.