It connects Kōhoku Station in Kōhoku, Saga Prefecture to Sasebo Station in Sasebo, Nagasaki Prefecture.

It is part of the route connecting Sasebo with Saga and Fukuoka.

From 1898 to 1934 the Kōhoku - Haiki section was part of the original Nagasaki Main Line.

The Kyushu Railway Co. opened the Yamaguchi (present-day Kōhoku) - Takeo (present-day Takeo-Onsen) section in 1895 as part of the original Nagasaki Main Line.

The section between Takahashi station and Omachi station will be double-tracked as the current compromise until the construction of the Kyushu Shinkansen Nagasaki route between Takeo-Onsen and Shin-Tosu can be decided.