Swine influenza is an acute respiratory disease prevalent in pig-growing areas all around the world and plays the roles of an intermediate host to be transmitted to mammals including human beings through a genetic recombination with the avian influenza virus. Recognizing that people could be contracted with swine influenza, this study set out to investigate the seroprevalence of individual and multiple infections with two subtypes (H1N1 and H3N2) of the swine influenza virus in pig farms in the Gyeongnam region according to age, area, and season, as well as to provide basic data for the prevention and control of swine influenza. Used in the study were total 904 swine sera that were not vaccinated against the influenza gathered from the pig farms in the Gyeongnam region from November, 2009 to October, 2010. HerdChek SIV (H1N1, H3N2) ELISA kit (IDEXX Laboratories, USA) was used for antibody testing against swine influenza. The test results show that 370 sera (40.9%) were infected with either H1N1 or H3N2 with 37.3% (337 sera) being contracted with H1N1, 13.1% (118 sera) with H3N2, and 9.4% (85) with both H1N1 and H3N2.