Eggs of Korean rose bitterling Rhodeus uyekii were collected and fertilized to observe temperature-related cleavage rates and mitotic intervals (${ au}_0$). As the water temperature was increased, the slope of first cleavage frequency with elapsed time after fertilization increased, and approximately 30% of fertilized eggs reached first cleavage frequency at every 15 min. At higher temperatures, eggs developed faster and underwent further identical developmental processes. There were strong, negative correlations between ${ au}_0$ and water temperatures at all temperatures studied (Y = -1.225X + 70.05, $r^2=0.988$, where Y is ${ au}_0$ and X is temperature).