A refrigeration unit is provided without impairing freshness, as before freezing, after thawing frozen subjects, and, with providing excellent color of dark colored flesh of fish/meat, especially in the case of using perishable food, such as meat or fish, for subjects to be frozen. A core unit for a refrigerator, between a substantially-rectangular first plate member and a substantially-rectangular second plate member spaced apart and arranged in parallel toward each other, where an electric wave is propagated to the sides of the first plate member and the second plate member by an electric wave transmission antenna, and that can form a unidirectional and substantially-uniform static magnetic field in substantially-normal directions of a principal surface of the first plate member and a principal surface of the second plate member, is used.