The invention relates to a packaging box having heat-retaining and cold-retaining functions that comprises: a main box body consisting of a side-surface part in which side surfaces are formed by folding and securing four side walls so as to form a space in which contents can be held, a floor part which respectively extends from the bottom parts of the four side walls in such a way as to form a floor surface, and lid parts which respectively extend from the top parts of the four side walls in such a way as to cover the upper side of the side-surface part in openable and closable fashion; and foamed paper which protects the contents held inside the main box body from external shock, and is provided inside the main box body so as to maintain heat retention and cold retention.