Monthly Screening of Pacific oyster, Crassostrea gigas, was surveyed by PCR for Ostreid herpesvirus(OsHV-1) infections from 2012 to 2013 in Korea. It was showed positive results in one hatchery in April and May 2012 and in oyster farming areas from August to November in 2013. The obtained sequences showed 99.3~99.5% homology with OsHV-1 ${mu}var$(Accession Number: HQ842610) and 96.2~96.3% homology with OsHV isolated from Korea(Accession Number: AY509253).