In Korea, the value of insect resources has been increased immensely and the insect industry is expected to increase up to 40 billion dollars by 2020. Among them, Korean horn beetle, Allomyrina dichotoma, is one of the strongest candidates for insect industry as medicinal purpose for various liver diseases and diabetes. In many local farms rearing larvae, a few bacterial and fungal pathogens causing disease of A. dichotoma larvae have been identified including Bacillus thuringiensis and Metarhizium anisopliae. For past few years, a disease seemingly due to viral infection has been reported for causing death of larvae en masse. The pathogen of this disease has not been identified so far. In Southeastern Asia, Oryctes rhinoceros nudivirus (OrNV) is known to cause severe disease in coconut palm rhinoceros beetle, Oryctes rhinoceros, and is used as a biological control agent to reduce the pest population. Here, we report for the first time that OrNV may have landed on Korea and may be the major pathogen for the diseased larvae of A. dichotoma. After peroral inoculation with the purified virus extracted from the hemolymph of diseased larvae, we confirmed that over 60% of infected larvae perished in six weeks. This viral disease spreads very fast in many farms nationwide throughout Korea. This threat not only makes economic loss of local farms rearing larvae, but also may disturb the ecosystem by transmitting to wild A. dichotoma.