Promotion Exam for Officials(PEO, in short, henceforth) were originally set up not for newly appointed persons, but for low officials of under Downward Low-Third Ranks(or Tang-ha-kwan). It was the 3rd king, Tae-jong, who looked for talented bureaucrats after he acceded to the throne in order to strengthen his administrative power. This was the background in which the PEO system was introduced for the first time. According to the formal regulation, PEO was regularly given once every ten years. The whole count, however, tells us that there were 57 times over all 479 years from the first conduct in 1407 A.D.(the 7th year of Tae-jong reign) to the last one in 1886 A.D.(the 23rd year of Ko-jong reign). The average term interval, then, was 8.4 years which fact implies that there were some additions which did not respect the rule; such a reign as king Se-jong, king Seong-jong, king Joong-jong, and king Young-jo. The most frequent conduct or the peak of the PEO was observed in 15th century and then it gradually declined. At last, there were less than half percent of the average number of passers for PEO, particularly, recorded around 19th century. This is a sharp contrast with other conducts, along with cannonical Civil Exams(or Moon-kwa), which had a various kind of Extraordinary Exams(or Pyeol-si). The more number of passers rapidly increased as Civil Exams went to the more later period in Joseon dynasty. The additional conduct of PEO shows at least two characteristics. In the first place, it was a king himself who was eager to tie closely with his supportive officials. This was a core reason of Selection-Exam-of-Gifted(or Pal-young-si) and Picking-up-Exam-of-Talented(or Teung-jun-si) which were originated in 1446 A.D., after the 7th king, Se-jo, conquered the opponents completely to be enthroned. The habitual conducts for PEO made it possible to be called Palace-Garden-Exam for Civil-Officials(or Moon-sin-jeong-si) comprehensively in "the Revised Version of Constitutive Law"(or Sok-tae-jon). This revision also allowed Upward-High-Third-Ranks(or Tang -sang-kwan) to take the exams too. For instance, the 21st king, Yoeng-jo, declared Picking-up-Exam-of-Talented in 1466 A.D. which Low-First-Ranks officials were, for the first time, permitted to take. Secondly, it was a good tool for a king to find loyal officials to get involved in a political renovation or revolution from time to time, in particular, such a reign as the 9th king, Seong-jong, and the 11th king Joong-jong. The former issued PEO twice even in a single period between 1477 and 1487 A.D., and the latter aimed a political reformation through Picking-up Exam. The analysis of former job careers for the whole passers in Joseon dynasty reveals that there were 7.3% of Upward -High-Third-Ranks(or Tang-sang-kwan), 65.7% of Low-Sixth -to-High-Third-Ranks(or Cham-sang-kwan), 17.3% of Down -ward-High-Seventh-Ranks(or Cham-ha-kwan), 7.1% of former officials(or Jeon-ham-kwan), and 2.6% of passers of Civil-Examinations and/or Temporary-Service-Members(or Keup-je and/or Kwon-ji). Among them, Low-Sixth -to-High-Third-Ranks(or Cham-sang-kwan) occupied the major portion. The detailed analysis on Low-Sixth-to-High-Third Ranks(or Cham-sang-kwan) includes a various members such as administrative practitioners in charge from E-joeng-pu, Six Ministries, and Each Subdivision Attached; Critical Inspectors from Hong-moon-kwan, Sa-kan-won, and Sa-heon-pu; teaching members from Seong-kyun-kwan, Se-ja-si -kang-won, and Jong-hak; former officials, military officials, and others. The 64.2% of Cham-sang-kwan were filled with officials of Fifth Rank and Sixth Rank. The half of this number, moreover, were from Six Ministries(or Yuk-jo) and Hong -moon-kwan. The highest position, Upward-High-Third-Ranks(or Tang-sang-kwan), was given to the PEO passers. Each category of the former positions shows a different ratio out of the same category to achieve the ultimate promotion; 71.4% of passers from Low-Sixth-to-High-Third Ranks(or Cham-sang-kwan) attained the goal; 43.9% of Downward-High-Seventh-Ranks(or Cham-ha-kwan), 86.2% of former officials, and 41.7% of Civil-Exams and/or Temporary-Service-Members(or Keup-je and/or Kwon-ji) each. It is said roughly that 66% of all the PEO passers were advanced to the position. This resulted in the large portion of high officials, that is, about 66.5% of Upward-2ndRanks, who took part in decision making procedures in their offices. The most salient portion against the general organization numbers was filled with PEO passers especially in Six Ministries so that they were the majority; Ei-jeong-pu, Sa-heon-pu, Sa-kan-won, Hong-moon-kwan, and Seong-kyun-kwan also reflected the same trend. This means that the passers of PEO were the core bureaucrats in Joseon dynasty.