Oppert Incident - an attempt to open the tomb of Prince Namyeongun, father of Daewongun, the regent of Joseon, by the expedition of merchant-traveler Jacob Ernst Oppert in the second half of the 19th century. This event is well known, however, there are several outstanding points. One of them is the incident exact date. Researchers indicate 1866, 1867 and 1868 as the date of the E. Oppert expedition. This article aim is to find out the exact date of the Oppert Incident. This paper used a variety of sources, such as the works of travelers, official documents, E. Oppert’s “Forbidden land: voyages to the Corea”. In conclusions, the author finds the Oppert Incident exact date, based on an analysis of sources and literature.