The pine wilt disease that blocks the path for water and nutrition in pine trees is caused by the nematode, Bursaphelenchus xylophilus (Nematoda: Aphelenchoididae). The nematode relies on the longhorn pine sawyer beetle Monochamus alternatus and Monochamus saltuaris (Coleoptera: Cerambycidae) as vectors. Recently, 2-(undecyloxy)ethanol was identified as a male-produced aggregation pheromone of Monochamus species. In this study, we investigated the effect of 2-(undecyloxy) ethanol along with host plant volatiles -pinene and ethanol on attracting M. alternatus at a pine forest in Pohang, Korea from May, 2014 to July, 2014. To sustain the volatility of 2-(undecyloxy)ethanol and host plant volatiles, a superabsorbent polymer based on polyacrylic acids and water were added to the pheromone mixture. A total of 46 M. alternatus were collected from two field bioassays. Our results indicate that 2-(undecyloxy)ethanol is effective in attracting M. alternatus in Korea. Our study suggests that the aggregation pheromone could be used for detection and population monitoring of the beetles as well as for the effective mass trapping in outbreak situations.