Following testing of a two-car prototype in the late 1980s, the 12-000 series was introduced into service in December 1991.

A total of 53 eight-car 12-000 series sets were built between 1990 and 2000 by Nippon Sharyo and Hitachi.

These cars had stainless steel bodies and were originally built with conventional traction motors.

[2] By 2001, a total of 424 vehicles were built by Nippon Sharyo and Hitachi, formed as 53 eight-car sets.

[4] The two prototype cars, 12-001 and 12-002, are preserved at Chihaya Flower Park in Toshima, Tokyo.