4) opened on 11 December 1961, initially running between Ōsakakō and Bentenchō (this was the first elevated portion of the Osaka subway system); trains were initially composed of single-car trainsets, with occasional use of three-car trainsets during trade fairs held near Asashiobashi.

The Keihanna Line was extended further into Nara when the extension to Gakken Nara-Tomigaoka opened on 27 March 2006.

Separately, a new station is planned to be built on the spur track to the Morinomiya depot facility as part of local revitalization efforts and also to serve the new Morinomiya campus of Osaka Metropolitan University, with a projected completion date of 2028.

In addition, all rolling stock are equipped with retarders to negotiate the continuous gradients of the Ikoma Tunnel of the Keihanna Line.

Since 2016, after heavier repairs and maintainence of all third-rail-powered Osaka Metro rolling stock have been consolidated at Midorigi Depot on the Yotsubashi Line, Chūō Line rolling stock owned by Osaka Metro are also able to access said depot via a newly-built spur track located before Hommachi Station.