The potato tuber moth (PTM, Phthorimaea operculella (Zeller)) is a serious pest of potato (Solanum tuberosum L.) plants in the field in regions with warm temperate to tropical climates, and of tubers stored under ambient temperatures post-harvest. Although PTM can be a minor to serious pest depending on the area and year, this pest is getting more and more serious to potato fields in Korea according to accidental surveys. Son (1979) represented 12.5℃ of average annual temperature as northern limit of distribution where corresponding to Youngdeog, Dalseong, Boseong and Jindo regions. Soon after, Choi and Park (1980) reported that the northern limit of PTM distribution coincided with -8℃ isotherm for average annual minimum temperature of January. In recent years, concerns on PTM occurrence and damage to potato are increasing due to climate change resulted in global warming. We carried out an extensive survey of PTM distribution using sex pheromone traps at 24 sites across the nation in 2009. As a result, we confirmed that the northern limit of PTM distribution climbed to southern Gyeonggi and middle Gangwon regions from Gyeongbuk and Chungbuk regions indicated by Choi and Park (1980). Hereafter, we are trying to investigate why drastic going northward of PTM happened in Korea. Here is one presumption that a sudden rise in average temperature has occurred during 30 years, from 6.34℃ in 1973 to 7.62℃ in 2007, especially around Daegwallyeong area where is a typical highland with 800 m high.