From earlier ages, Koreans called the structure as Chomsongdae Observatory which observed the celestial body and studied astronomy with astronomical instruments. They began the observation and recording of the astronomy and meteorology already in the time of Ancient Joson and from the time of the Three Kingdoms they positioned the governmental department and officials in charge of the astronomy and meteorology to perform such observations in earnest. Koguryo dynasty had even had made use of an astronomical chart. The remains of the old observatories are still kept, which tell the advanced level of the astronomy at the time. There was a Chomsongdae Observatory in Pyongyang in the Koguryo time. The Chomsongdae Observatory in Kyongju, North Kyongsang Province still remaining had been built in the first half of the 7th century. It is the oldest of its kind in the world. It shows the level of the scientific development of the time. The Korean historical records contain many astronomical and meteorological materials which were comparatively elaborate. The astronomical chart chonsangryolchabunyajido, the prototype of which was made in the Koguryo time, had 1 467 stars in 282 constellations precisely positioned, comparatively, in their proper place round the North Pole. That is the proof of the high level of the development of the astronomic observation of the time.