The present invention provides a freshness preservation method and a freshness preservation bag that enables to keep freshness of a vegetable, fruit or fresh flower for a long period. A storage bag 10 is formed by a nonporous film 1. Non-adhesive portions are continuously formed on a heat sealed portion 11 of the storage bag 10. The non-adhesive portions function as the vent holes 2 communicating with the outside of the storage bag 10. The carbon dioxide generated from the vegetable, fruit or fresh flower in the storage bag 10 is discharged from the vent holes 2. The oxygen of the outside is shut off by the vent holes 2. The vegetable, fruit or fresh flower is allowed to breath only by the oxygen sealed in the storage bag 10. An oxygen concentration is gradually reduced according to a degree of breathing of each of the vegetable, fruit or fresh flower.
