Lymphocystis disease virus (LCDV) is the causative agent of lymphocystis disease. The viruses have been divided into three genotypes (genotype I for LCDV-1, II for Japanese flounder isolates, and III for rockfish isolates) on the basis of major capsid protein (MCP) gene sequences. In this study, we developed a multiplex PCR primer set in order to distinguish these genotypes. We also analyzed the MCP gene of a new LCDV isolate from the sea bass (SB98Yosu). Comparison of sequence identities between SB98Yosu and eight Japanese flounder isolates, revealed identity of more than 90.1 % at nucleotide level and 96.5% at deduced amino acid level, respectively. Phylogenetic analyses based on the MCP gene showed that SB98Yosu belongs to genotype II, along with Japanese flounder isolates. Multiplex PCR based on the MCP gene allowed us to identify these genotypes in a simple and rapid manner, even in a sample that contained two genotypes, in this case genotypes II and III.