The first section of what is now this line was opened by Tateyama Light Railway as a 762 mm (2 ft 6 in) gauge line between Gohyakkoku (on the Toyama Chiho Railway Tateyama Line) and Namerikawa in 1913.[citation needed]
The Kurobe Railway opened the Dentetsu Kurobe to Unazuki Onsen section as a 1,067 mm (3 ft 6 in) gauge line between 1922 and 1923.[citation needed]
In 1932, the Toyama Electric Railway acquired the Tateyama Light Railway, and built a line from Dentetsu-Toyama to Namerikawa, regauging some of the original line to 1,067 mm gauge, and electrifying it at 1,500 V DC.[citation needed]
The Namerikawa to Dentetsu Kurobe section was opened between 1935 and 1936, and the Kurobe Railway was merged with the Toyama Electric Railway in 1943 to create the current company, with the electrification to Unazuki Onsen commissioned the same year.[citation needed]
CTC signalling was commissioned on the line between 1966 and 1967, and the Dentetsu-Toyama to Inarimachi section was double-tracked in 1969.[citation needed] Freight services ceased in 1983.[citation needed]