Up to date several mycoviruses including Spherical Virus (LeSV) have been reported. As fungal virus was spreaded by infested hypae and spores it could be important to use virus-free spawns to eradicate the mushroom virus disease in the culture farm. We tested the imported spawns of by PCR whether LeSV was infested them or not. The primer set targeting the RdRp gene of LeSV was prepared based on partial sequence of the LeSV genome. The RT-PCR analysis showed that 87 among 88 imported spawns of were infested by LeSV.