This paper examines Haniwa costume in the Goboon period of Japan. The results are as follows. 1. Haniwa costume consisted of two pieces, the upper one and the lower one. Man wore Jacket and Pants, woman wore Jacket and Skirt ; besides, they wore several ornaments such as hats, necklaces, earings, bracelets. 2. When it was introduced, two-piece costume signified, symbolically, the authority of the chieftain and his near men wore it. 3. Before it was introduced, their proper costume had been the same kind of costume as Whoengpok-costume and Gwandu-costume, which was the primitive costume in the South countries. That costume was fit both for the hot and wet nature of Japan and for the working lower-class, so it was continuously worn by the lower-class after two-piece costume had been introduced. 4. In the Goboon period of Japan, a unified government with the class ruling was established for the first time. Thus, this social order was reflected in costume as a whole, and costume had such class-oriented features.