Japan is switching off its last working nuclear reactor, as part of the safety drive since the March 2011 tsunami triggered a meltdown at the Fukushima plant.
The third reactor at the Tomari plant, in Hokkaido prefecture, is shutting down for routine maintenance.
It leaves Japan without energy from atomic power for the first time for more than 40 years.
Until last year, Japan got 30% of its power from nuclear energy.
Hundreds of people marched through Tokyo, waving banners to celebrate what they hope will be the end of nuclear power in Japan.