A sealing member is applied to the surface of a liquid storage container having a liquid supply port provided so as to be open to a concave space formed on the surface with a gap between the applied sealing member and the liquid supply ports so as to seal the concave space. The liquid supply port has a profile adapted to be inserted into and connected to a connecting portion for supplying liquid to the liquid supply port. A cut score section is formed on the sealing member as including a center point located at the position on the extension from the front end of the liquid supply port in the direction of connecting the liquid supply port to the connecting portion and the cut score section is torn as it is pressed by the connecting portion moving toward the liquid supply port.