The line was originally built and operated by the between Katamachi and Shijōnawate in 1895. Two years later, the
Kansai Railway bought the line in order to have its own trunk line to Osaka from Nagoya, combined with constructing the section between Shijōnawate and Kizu. Katamachi Station was unable to be expanded, thus Amijima terminus was constructed. However Kansai Railway bought the line from Nara via Ōji to Minatomachi (present ) in downtown Osaka, and shifted its main line to the ex-Naniwa Railway line. Thereafter, the Katamachi Line became a branch of the railway network of Osaka. The Shigino to Hanaten section was duplicated in 1927, with the Katamachi to Shigino section double-tracked in 1955, the Hanaten to Shijonawate section in 1969, extended to Nagao in 1979, to Matsuiyamate in 1989, and the balance of the section to Kyobashi double-tracked between 2007 and 2009. The section between Katamachi and Shijōnawate became the first
Japan Governmental Railways electrified line in Osaka-Kobe-Kyoto area in 1932, with electrification extended to Nagao in 1950. After privatization of the then
Japanese National Railways (JNR), the line became part of the
West Japan Railway Company (JR West) system, and the Kizu to Nagao section was electrified in 1989. In 1997, the
JR Tōzai Line was opened and connected to Katamachi Line at Kyōbashi, and Katamachi Station was closed (with
Ōsakajō-kitazume Station becoming the replacement station). Most trains began operating through to the
Fukuchiyama Line (
JR Takarazuka Line). Converted from a freight branch to a passenger route, the
Osaka Higashi Line began service in 2008. Trains from Nara via
Kansai Main (
Yamatoji) Line began operation to Amagasaki Station. However, these through trains to Amagasaki have now ceased operation since March 2019, with the Osaka Higashi Line extension. Station numbering was introduced to the line in March 2018 with stops being assigned station numbers between JR-H18 and JR-H41.
Military use Three military/weapons-related facilities used during the early 20th century were serviced by spurs located between and
Tsuda Stations (Kin-ya Ammunition Dump, where two explosions occurred in 1909 and 1939), between and
Hoshida Stations (Uji Weapon Kori Factory), and the Osaka Army Arsenal warehouse between and
Shigino Stations. ==Route and operation==