They came from another site nearby where around 1,000 people have been living in miserable conditions with limited protection from the cold.
The new camp, featuring some 200 heated wooden cabins and proper toilets and showers, has been built by Doctors Without Borders (MSF) with the support of the local town hall, despite opposition from the French government.
The 3.1 million euro ($3.4 million) migrant accommodation is thought to be the first in France to meet international standards, and MSF said they hoped soon to have 375 cabins, catering for 2,500 people.
"It's a great day for human solidarity," said local mayor Damien Careme, who fought a battle with the authorities.
"I've overcome a failure of the state," he said, adding that he could no longer stand the sight of around 75 children living in the original camp.
The move has frustrated the government which has been trying to move refugees away from the northern coast and into centres where their movement is more controlled.
The government's representative in northern France, Jean-Francois Cordet, said last month: "The government's policy is not to reconstitute a camp at Grande-Synthe, but to make it go away."
The authorities began a second week of demolition at the region's largest refugee camp, nicknamed the "Jungle", in nearby Calais on Monday.
Thousands of migrants have been living in the Jungle and other smaller camps along the northern coast, desperate to reach Britain where many have family or community ties and see better hopes of gaining employment or education.
Most have turned down offers from the French government to move into heated containers alongside the Jungle, or into accommodation centres elsewhere in France.