Japan has made it illegal to go within 20km of the nuclear power plant damaged in the March 11 earthquake.
Thousands of people left the area around the Fukushima plant following the quake.
Those living in the evacuation zone have now been told it's illegal for them to stay there, although they're allowed home to get their belongings.
Officials are worried the radiation around the plant could be dangerous and don't want anyone to get too close.
JAPAN PICTURES: One month after the quake
Around 80,000 people live in the 20km evacuation zone, but most of them have already left.
It's thought at least 60 families are still living in the area around the plant.
The 11 March earthquake and tsunami damaged the cooling systems in the nuclear power plant, and radiation has been leaking from the plant ever since.
Anyone who goes back into the evacuation zone could be fined, or put in prison for up to 30 days.