We relocated the mainshock and its aftershocks of the 1944 Tonankai earthquake (M 7.9) using the modified joint hypocenter determination (MJHD) method in order to obtain their accurate hypocenters and to identify the fault plane of the mainshock. We used both P- and S-wave initial arrival times at stations worldwide reported by the Japan Meteorological Agency (JMA) and International Seismological Summary (ISS). We confirmed by relocated hypocenters that the mainshock and many direct aftershocks had occurred along the plate boundary between the Eurasian and Philippine Sea plates. We also confirmed that the eastern end of the aftershock area reached the Tenryu River, where induced shallow crustal earthquakes also occurred. The aftershocks south of Shionomisaki and along the SE coast of the Kii Peninsula are crustal earthquakes induced by the mainshock.