The occurrence of heat waves estimated on historical runs of climate change was compared to that on reanalysis data from 1981 to 2005. Heat waves in the future then were predicted on the basis of climate change scenarios from 2006 to 2100. For the past period, the heat wave days predicted from the climate change scenarios data overestimated and than those by the reanalysis data. For the future period, the heat wave days increased until the mid-21st century and then stay stagnant by the RCP 2.6 scenario. However, the yearly heat wave days steadily increased until 2100 by the RCP 8.5 scenario. The synoptic cause of the most severe year of the heat wave days was analyzed as a strong high pressure developed around the Korean peninsula. The high pressure under the RCP 2.6 scenario was caused by the high level jet stream in the border area between China and Russia, whereas the high pressure under the RCP 8.5 scenario was caused by the strong high level jet stream and pressure ridge in the East Sea.