An ink cartridge serving as a liquid container, comprises a liquid sensor having a piezoelectric element which detects a consumption state of the liquid contained in the container, and a consumption data memory as a memory means. The consumption data memory is a rewritable memory which stores consumption related data which are related to the detection of the consumption state using the liquid sensor. The consumption related data are, for example, consumption state data as a result of the detection. Even when the ink cartridge is removed, the consumption state data can still be utilized. The consumption related data may be a detection characteristic detected depending on the consumption state of the liquid. Based on this detection characteristic, the consumption state is detected utilizing the liquid sensor. The consumption state can be detected irrespective of individual differences of the ink cartridges.