This study examines ozone episodes occurred during the intensive sampling periods (Jun. 1-30, 2004) in the air of Seoul metropolitan area. During that period, there were 8 events (or days) in which 1 hr averaged ozone concentrations were greater than 100 ppbv. The photochemical analysis of ozone chemistry (i.e., budget and formation and destruction strengths of ozone) was carried out using a photochemical box model. Peaks in diurnal ozone variations during ozone episode periods occurred were concurrent with the sudden change of the slope of $NO_{2}/NO$ ratio, suggesting significant correlation with photochemical reactivity. In addition, the ozone peaks were concurrent with high concentrations of ozone precursors, peroxy radicals of $HO_{2},;CH_{3}O_{2},;and;RO_{2}$. High ozone levels during the ozone episodes are likely to be affected by ozone destruction rate.