According to one aspect of the invention, a remanufacturing method of a liquid container forms an inlet in a certain area, for example, a buffer chamber, other than a specific section including liquid reservoirs and flow paths adjoining to and directly communicating with a bubble trap flow path in the liquid container. In the state of closing a liquid feeder and opening an air open structure, the remanufacturing method injects a liquid through the inlet to fill a space in the upstream of the inlet with the liquid. In the state of opening the liquid feeder and closing the air open structure, the remanufacturing method injects the liquid through the inlet to fill a space in the downstream of the inlet with the liquid. The remanufacturing process seals the inlet after completion of the injection of the liquid. This arrangement enables the liquid to be refilled into the liquid container without damaging the functions of the liquid container.