To develop an empirical degree-day model for predicting the spring flight period of the bark beetle, Ips subelongatus Motschulsky, based on field observation, field studies were biweekly conducted in three Japanese larch (Larix kaempferi) forests in In-je, Korea from 2013 to 2014. To validate this degree-day model, we compared the model-predicted values with observed emergence data of I. subelongatus in 2015 spring at one of the sites. The flight period of over-wintering generation began on April and ended May, and flight of next generation lasted until October. The lower developmental threshold temperature (LDT) was estimated using spring emergence of I. subelongatus and field temperatures. Then a degree-day model was constructed, based on LDTs estimated from field observations data. The baseline temperature with the highest coefficient of determination was considered the LDT, and this was estimated to be 6.0℃. The explanatory power of the model was 88%. This model accurately predicted the flight of I. subelongatus in 2015 spring, as the estimated median flight dates was 1 days earlier than the corresponding observed flight date. The results of the goodness-of-fit test did not differ between observed and estimated values (ks = 0.21, P = 0.54).