This study explores a wide range of issues including typical attributes, distribution, history, uniqueness of Korean folktales, symbols, influx routes and transformation of Why the Sea is Salty(AT 565). For this purpose, this study investigated folktales of the world and neighboring countries and compared the composition and composing factors of Korean folktales with those of Japanese folktales which show similarities with Korean ones. The typical attribute of this folktale, which shows worldwide distribution, is development of the story in 3 different directions, which is 'delicious porridge(KHM 103)', 'the man who stole the mill called the master to stop' and 'a captain produced salt on the ship, had his ship sunk because he did not know how to stop the mill and the mill keeps producing salt, which is the reason why the sea is salty.' Its origin dates back to Chinese myth Water Goddess Shuimu Niangniang(水母娘娘) and northern European myth Grottas?ngr or the Song of Gr?tti and bibliographical record for the former can be found in Baishi Huibian(稗史彙編) of Ming Dynasty(明代) while the that for the latter are shown in Elder Edda and Snorra Edda. The Korean folktales show 3rd type of development. They are composed of acquisition and loss of the mill(opponent 1), reclamation and loss of the mill(opponent 2) and the reason why the sea is salty and have been passed down in oral tradition in C type with all the motifs, A type with the omission of acquisition, reclamation and loss(opponent 2) of the mill, B and D type with the omission of only reclamation and loss of the mill and E type with the omission of the reason why the sea is salty. B type exhibits the attribute that the giver donates the mill to the proponent with good character and D type has both helper and giver and has the peculiarity that the giver is adwarf. Type A is the simplest in composition and has been collected most frequently followed by type C. Type b corresponding to type B is the majority in Japanese folktales followed by type c corresponding to type C. Korean type C is closer to European types, whereas type D is similar to Japanese ones. These two types are presumed to have flowed in during the Japanese Colonial Period through European-style Japanese translation and became Koreanized. Type A has the room to assume other routes of delivery, probably through mainland China, considering the simplicity of composition, uniqueness of factors and existence in Pyeognbuk and Hamnam areas. Type B and E have undergone transformation within the bounds of Korean peninsula. The magic mill playing pivotal role in this tale works wonders of wealth for the good and warns the jealous, the greedy and those who pursue a quick fortune by sinking them under the deep sea. Still the mill itself maintains and enriches our life by continuing to work to produce precious salt. It has passed down through generations as a symbol of production and abundance so that we can beat the evil and lead affluent lives.