Police say five cakes of plastic explosives, two detonators and two automatic weapons including a machine gun were found in his car, which was parked at the airport.
The suspect, named as Abderazak Besseghir, has no criminal record and is not known to have any links with any Islamic militant groups.
The BBC's correspondent in Paris says it is not clear what, if any, action was planned.
But he adds that possible terrorist links will be among the first theories tackled by investigators.
Mr Besseghir is a Frenchman of Algerian descent. As a baggage handler, he has security clearance for several restricted areas of Charles de Gaulle airport, one of Europe's busiest.
It was from Charles de Gaulle last year that shoe-bomber Richard Reid left on a flight to Miami which he later tried to blow up, in support of al-Qaeda leader Osama Bin Laden.
Tip-off
Police say Mr Besseghir, 27, is refusing to talk to investigators, except to say he suspects a plot against him.
He was arrested late on Saturday after a tip-off from a member of the public, who saw a weapon in the car boot.
Police later found the rest of the weapons cache, which sources say included a bomb that was "ready to use".
One report said police believed it was possible that a hijacking was being planned.
But Mr Besseghir has said someone else must have put the weapons and explosives in his car as he had no knowledge of them.
The suspect's apartment in the northern Parisian suburb of Bondy has been searched.
His father, two brothers and a family friend have also been taken in for questioning. But they have not shed light on the matter, reports from Paris say.
Mr Besseghir can be held for up to four days without charge.
Security effort
Paris police have made several arrests in the past two weeks of suspected Islamic militants. The authorities say some were planning an attack on the Russian embassy in the city.
Police said before Christmas that they had found bomb-making equipment during raids in the Paris suburbs.
In total, nine arrests have been made since 16 December, when four people were arrested in the Paris suburb of La Courneuve.
All those arrested are said to be of Algerian or Moroccan origin.
The arrests stem from an investigation into possible connections between Islamic militants in Europe and Chechnya.
Fearing a possible attack over the Christmas and New Year holiday period, the French Government has ordered an extra 1,000 police and troops on to the streets of Paris.