Paris — Shaggy-haired, jeans-clad youths may dominate the public's perception of the typical peacenik, but here in France things are different. Meet Michel Langignon, the leader of the Mouvement de la Paix. He is 60 years old and a picture of gray: gray flannel pants, gray woolen sweater, gray thinning hair, and a grayish complexion. He is also a committed member of the Communist Party.
''I've been a member of the peace movement since its beginning in 1949,'' he says. ''I remember working with Jean-Paul Sartre, Pablo Picasso, and Yves Montand. In 1950, we collected 14 million signatures for the Stockholm call for nuclear disarmament.''
Since then, the French peace movement has lost much of its luster, becoming today the weakest link in the chain of European peace protests. Many of Mr. Langignon's old comrades have either passed on or defected; and, mainly because of continuing Communist ties with the Mouve-ment de la Paix, peaceniks here are divided.
Mr. Langignon's Communist-supported group held a demonstration Oct. 22 and the noncommunist Committee for Nuclear Disarmament in Europe (CODENE) held another march the next day. Each rally drew relatively listless crowds of only about 10,000 marchers.
''The Germans are way ahead of us,'' he admits. ''That's because the Pershings are being installed there, not here.''
Mr. Langignon has a point. France is not part of NATO's integrated military command. It is the French President who would pull the trigger on his country's independent nuclear force.
But a quick look at Mr. Langignon's life suggests other reasons for the weakness of pacifism here, and how a communist-inspired peace movement has gone from a powerful force to an impotent, almost irrelevant one.
Mr. Langignon joined the Communist Party in 1943. Instead of going to Germany to work in war factories, he wanted to fight the occupiers.
''The Communists were the only ones fighting back,'' he explains. ''Only the Communists stood for freedom.''
With Communists making up the backbone of the resistance, a generation of Frenchmen grew up sharing Langignon's belief. After the war, Langignon went to work full-time for the Mouvement de la Paix.
His colleagues were numerous and brilliant. He points to an original Picasso peace dove on his office wall. Sartre wrote tracts for the group's newspaper. Montand gave benefit concerts.
It used to be that demonstrations were mass affairs. ''One time during the Algerian war we filled the entire Champs Elysees,'' he says. ''The police were so scared.''
Then the world turned upside down. Soviet tanks rumbled in Prague, Solzhenitsyn exposed the gulag, and Russia's heavy hand was felt in Afghanistan, Poland, and most recently, in the Korean airliner tragedy. The Mouvement de la Paix followed the Kremlin each time.
So when the Euromissile issue emerged and the Mouvement de la Paix jumped on the bandwagon, relatively few Frenchmen were willing to follow.
Among French political parties, only fellow Communists accept Langignon's thesis that Soviet SS-20s present no threat, that East-West nuclear forces in Europe are ''balanced,'' that ''Reagan should have jumped at Andropov's arms control suggestions,'' and that ''America doesn't really want to negotiate arms control.''
Even the governing French Socialist Party, long a haven for pacifism, believes this is rubbish. It is firmly behind tha decision to install NATO Euromissiles.
Langignon infuriates most Frenchmen by calling for the inclusion of the country's nuclear force in the Geneva talks. This is a major Soviet demand, but again only the French Communists can stomach it.
All the other political parties refuse. They agree with President Francois Mitterrand when he argues that the nuclear force de frappe is the key to France's independence. The public agrees as well: Polls show that two-thirds of the French people believe France's nuclear deterrent is ''positive.''
That leaves one-third uneasy with nuclear weapons. But many of these potential converts are not Communists and could not accept Langignon's leadership.
CODENE, the noncommunist peace group, is working to enroll these noncommunist pacifists. So far it has had only minimal success, but it sees signs that French youth are disillusioned with the US nuclear umbrella.
Langignon's group, meanwhile, is becoming more and more dependent on the Communists for its money and members. This leaves the graying peacenik in a sullen mood. He expresses his positions without enthusiasm.
Next year, he plans to retire and write his memoirs. He is getting too old for activism, he says.
CODENE's leader, Michel Leter, agrees. He decries Langignon's group for being tools of the Soviets and says they must go if pacifism is to take off in France.
''We must be independent,'' he says. Langignon ''is part of another era.''