The class 1000 EMUs were built between 1972 and 1997 for Seoul Subway Line 1. As South Korea did not have experiences in the design and manufacturing of EMUs at that time, Japanese manufacturers took over. The electric part was taken from the JNR class 415, while the design of the carbody came from the class 301. On the Seoul Metro section these trains operated at 1,500 V DC, what changed do 25,000 V AC on the national Korail network.

Korean manufacturers took over in 1976. Multiple generations were built over the years, which also differed in the appearance of the front ends. Originally the sets consisted of six cars each and were first lengthened to eight and then ten cars. While the six-car sets had four powered cars, the longer sets had six. The oldest were retired in the late nineties and the last ones followed by 2020.