Japanese Government Railways (JGR), designated the track as the Hōshū Main Line on 12 October 1909 and expanded it southwards in phases over the next 13 years, establishing Shigeoka as its southern terminus on 26 March 1922.

The link up between the two lines was achieved on 15 December 1923, establishing through traffic from Kokura in the north to Miyakonojō.

On the same day, Sōtarō was opened as a signal box on the linking track.

With the privatization of Japanese National Railways (JNR), the successor of JGR, on 1 April 1987, the station came under the control of JR Kyushu.

[7] Media related to Sotaro Station at Wikimedia Commons This Oita Prefecture railroad station-related article is a stub.