Soft ticks, Argas vespertilionis, were collected from feces of bats in Japan. Cytopathic effect (CPE) was observed after inoculating the homogenates of ticks to Vero cells. Sequencing of RNA extracted from the cell supernatant was performed by next generation sequencer. The contigs had identity to segments of Bunyaviruses, Issyk-Kul virus. The identities of segment L, M and S were only 77, 76 and 79% to Issyk-Kul virus, respectively. Therefore, we named this novel virus Soft tick bunyavirus (STBV). In the phylogenetic tree, segment L of STBV was closely related to a cluster consisting of the genus Nairovirus of the family Bunyaviridae.