A large, catastrophic landslide took place on Ono area in Oita Prefecture, southwest Japan, triggered by extraordinarily heavy rain on July 5-6, 2017. Seismic waves triggered by this landslide were captured by high sensitivity seismometers in the routine seismic network. The signals consisted of two packets of seismic waves, and the latter one was found about one minute after the former with a longer duration and a slightly lower dominant frequency. The shape and the dominant frequency were consistent to those observed in the past landslide cases. The source location determined by using amplitude information presents small residuals with the real landslide site. The estimation accuracy was 5 km, considering the spread of the region with the small residuals. The durations and dominant frequencies of the two seismic signals suggested that the northern debris flow preceded the southern landslide rotational displacement, which was consistent with the geological insights of the past studies. This case study illustrates the possibility of the remote monitoring of the inland landslides with a size larger than 100－200 m by the permanent seismic network in Japan.