Speaking on the sidelines of the World Economic Forum in Davos on Thursday, Valls said he attended the gathering to speak about "all the dangers" which the bloc is facing.
Those dangers "could lead to a fracturing of the European project, and not in a few years or decades, but in the next few months," he said.
Valls mentioned the recent refugee inflow into the EU countries as one of the dangers that could cause the collapse of the bloc.
Europe has been facing an unprecedented inflow of refugees fleeing wars and violence in Africa and the Middle East, particularly Syria.
More than one million refugees entered Europe in 2015, according to the United Nations refugee agency, UNHCR.
Valls cited terrorism and a possible British exit from the bloc as other dangers threatening the EU.
He said a British exit from the bloc "would undoubtedly be a bad thing, a very bad thing."
However, he added that a deal that could keep Britain in the EU should not come at any price, noting it is unlikely to be struck at a pivotal summit of the bloc's leaders in February.
"There needs to be a deal, but not at any price," said the French PM.
A referendum on British membership of EU will be held by the end of 2017, Press TV reported.
S/SH