To manifest synergistic effects by treating a food with ozonized water or placing the food together with the ozonized water in a container, hermetically sealing the food therein, heating the hermetically sealed food under pressure or quick freezing or drying the food, thereby remarkably reduce the deterioration in flavor and taste of the food and enable the solution of an increase in keeping quality at the same time.

(1) This method for preserving a food comprises treating the food with ozonized water, then placing the resultant food in a container or placing the food therein together with the ozonized water therein, hermetically sealing the container and heating the hermetically sealed food under pressure. (2) The method for preserving the food comprises treating the food with the ozonized water and then quick freezing the treated food or quick freezing the food together with the ozonized water. (3) The method for preserving the food comprises treating the food with the ozonized water and then drying the treated food.