PURPOSE: To improve the taste of a thawed fish after thawing a frozen fish and further the keeping quality of both the freshness and a fresh color to better than that of a fresh product.

CONSTITUTION: This apparatus is equipped with a water tank 2 for housing constant cold water at about +2°C by using seawater or salt water, produced from natural salt and having the concentration and components comparable to those of the seawater, an air blower 3 and a bubble producer 7 for bubbling air from the air blower 3 in the water tank. Furthermore, an ion generator box 5 for converting the air into negative ions and including ozone therein is installed.