A liquid retainer support is arranged in a body of a liquid ejection apparatus in an immovable manner or in such a manner as to allow reciprocation of the liquid retainer support. A liquid retainer is secured to the liquid retainer support. A liquid retainer chamber is defined in the liquid retainer in such a manner as to allow communication between the liquid retainer chamber and the atmospheric air. A liquid supply system of the liquid ejection apparatus is manufactured by blocking the liquid retainer chamber from the atmospheric air and connecting a liquid passage defining body to the liquid retainer for supplying liquid from a liquid reservoir to the liquid retainer chamber. The liquid passage defining body includes a liquid passage that communicates with the liquid reservoir. In this manner, the cost for manufacturing the liquid supply system is reduced.