A packaging material is provided that can provide a packaging bag or container cover in which the contents is shielded from the atmosphere and tightly sealed, a small hole is formed in the appropriate locations, without special processing of the heat seal portion, and the internal pressure is maintained with high stability at a level above the normal pressure. The packaging material is suitable, for example, for heating in a microwave oven. The packaging material uses a film in which a heat sealing agent (4) with a low melting point is applied to a prescribed zone of an oriented film (2) made of a synthetic resin, a cutting line (5) is cut in the oriented film (2) made of a synthetic resin in the form of a solid or broken line passing through the zone coated with the heat sealing agent (4), and a cast film (3) made of a synthetic resin and having heat sealing properties is affixed to the oriented film (2) made of a synthetic resin. Such film is used for a packaging bag (1) or a container cover.