To dissipate volatized air when being heated by utilizing a heat- shrinkable sealing strip used by being wound on a packaging container.

A packaging container A is formed of a container main body 1 with a cover 2 covering the container main body, and a through-hole 20 is formed on a sealing strip zone of the cover 2, and a sealing strip 3, a part or the whole of which is heat-shrinkable to close the through-hole 20, is wound and tightened on the packaging container A by the heat shrinkage, and when being heated by a microwave oven or the like, the sealing strip 3 is pushed up from the through-hole 20 by the rise of internal pressure to communicate the through-hole 20 with the outside, and as the sealing strip 3, a sealing strip of the constitution in which only the lower side section of the packaging container A positioned on the bottom side is made to heat shrink along the strip direction is used, and only the lower side section of the sealing strip 3 is made to heat shrink along the strip direction to wind and tighten the sealing strip 3.