PURPOSE: To preserve a fermented food at room temperature comprising soybeans such as NATTO (fermented soybeans) or MISO (fermented soybean paste which are liable to accompany change by fermentation with time.

CONSTITUTION: A fermented food having completed fermentation process, comprising soybeans as a raw material is stored in a sealable container so that the fermented food is prevented from being in contact with air to stop further fermentation of the fermented food.