Four strains of Piptoporus betulinus were isolated from a trunk of the Betula ermani in Seorak mountain. These strains were studied to observe whether they are originated from the same genet or not, by using the method of pairing culture between strains and by comparing part of the nuclear rDNA of ITS regions amplified with NSI1 and ITS4B primers. The demarcation line was not formed on the potato dextrose agar plates in the combinations of two different strains. Partial nuclear rDNA sequences of the four strains were also the same. As a result, it is considered in high probability that they are derived from a single spawn.