"Sibeongron(時病論)" is a book that was written by Noepung(雷豐, Leifeng) in the latter period of Cheong(淸) dynasty. In this book, Noepung described the Siryeong(時令) disease by oegam(外感), and the theoretical tool he used to analyze the Siryeong disease was the Ungi(運氣) theory based on "Naegyeong(內經)". Based on the Ungi theory, Noepung(雷豐) classified the Siryeong(時令) disease into two groups of singam(新感) and bokgi(伏氣), so that his theory of Siryeong disease could successfully describe the Siryeong diseases of four seasons. To understand his theory of Siryeong disease, it is very important to understand the concept of the relation between the division of time and the etiological cause by oegam(外感). Based on this concept, this study will be analyzing how each Siryeong disease was defined in his etilogical view which had been originated from the Ungi(運氣) theory in "Naegyeong".