Udometer is a rainfall measuring instrument invented and used during the Joson Feudal Dynasty.

In Korea the rainfall was measured also during the Koryo Dynasty, a feudal state which existed between 918 and 1392.

According to a record, an iron udometer of cylinder shape was made in 1441, which was about 40 centimetres high and about 16 centimetres across. Later the udometer was manufactured several times in 1442, 1770 and so on.

Udometer, a vessel of cylinder shape put on a stand, received rainwater and its volume was measured. Similar ones were installed in the yards of the central and local government offices; they were made of iron or bronze in the central government office and of porcelain or earthenware in the local government offices.

The towns recorded the time when rain began and stopped and measured the amount of rainfall during the time and reported them to their provinces and the provinces reported it to the central astronomical and meteorological observation institute Soun House, which summed up and recorded it.

Such scientific method of measuring the amount of rainfall with udometer and the system of summing up the results of the measurement were the earliest one in the world. It was in 1639 that Italy measured the depth of rainwater with an instrument.

The udometer invented and used in Korea was about 200 years earlier than the Italian one.

It is a precious cultural legacy representing the creative talents of the Korean people.