This study is aimed at finding out the establishment and operation of office-post system( 官職制) shown in historical materials of Silla period The official rank system(官職制) and office-post system occupy an important position as an index which shows an establishment and a development of Silla society. The official rank system expressed an institutionalization of person's rank which participated in the operation of the society, while the office-post system indicated the post and the related institution which took charge of the personal order. Therefore, they are an essential element to understand the Silla society and a barometer that we can measure the standard of the development during.