A sub tank is provided that includes a case at which an air flow path is formed, the air flow path including an entrance flow path portion that is connected to an ink accommodating portion of the case, and a cross flow path portion that continues from the entrance flow path portion. The cross flow path portion extends in an upper diagonal direction with respect to a reference plane corresponding to the ink liquid level at a standstill state. Another sub tank is provided that includes a case forming an ink accommodating portion, on which case a flexible film member is attached through bonding or welding to seal an opening of the ink accommodating portion and to form one side of the sub tank. A spring is disposed within the ink accommodating portion between the case and the flexible film member, the spring forcing the flexible film member outward.