SOURCE
This incredible popular entertainment has been found out about 30 years ago in the city of Kobe, one of the three biggest cities in Kansai(Japan).

However other opinions say it was already known far before, between 1950 and 1960, and that it began with an American TV-show, according to that version TV-spectors sang following a ball jumping above the songtext on their TV-screen.

Appearently it was after that period that the Japanese made the Karaoke entertainment and for the first 20 years it only was there in Japan, later it came all over the world.

CURIOSITIES. THE "KARAOKE BOXES"
With the development of the Karaoke also sellings-problems came up because in that time most of the Japanese houses were made of wood, so singing at home in the evening was very disturbing for their neighbours. That's why the "karaoke boxes" were born.

These are acoustically isolated rooms, closed with a door, placed on roadsides where people can sing, without disturbing anybody else. The first "Karaoke box" was placed in 1984 in a rice camp of Prefectura de Okayama, in the eastern zone of Kansai. Later they became more comun, even nearby the cities, and in buildings, these last ones are individual soundproofed rooms. At present there are more than 100.000 "Karaoke boxes" in Japan.