a differential pressure valve unit that is accommodated in a liquid cartridge main body having : a liquid containing portion containing liquid ; and a liquid supply portion supplying the liquid in the liquid containing portion to the outside , the differential pressure value unit including : a membrane valve that is opened when a predetermined pressure difference between the liquid containing portion and the liquid supply portion occurs ; and a first member that holds the membrane valve and forms a downstream pressure chamber together with the membrane valve , wherein , in the first member , an opposing surface forming the downstream pressure chamber and having a connection port connected to the liquid supply portion has a shape corresponding to a movable range of the membrane valve , and a groove portion is provided at the opposing surface in order to allow the liquid in the downstream pressure chamber to easily flow into the connection port .