He began farming at a young age and at fourteen, he was a juvenile at Monceau-les-Mines. In 1898 in Paris, on a road construction site called Subway, he began to attend circles of unionists and anarchists.
He returned to Monceau-les-Mines in spring 1900 and continued to advocate for the anarcho-unionist movement. On June 2, 1900, after the death of a steelworker striker named Fog who was killed by the police, he declared, in a violent speech at the funeral: that Fog was arrested and convicted for "excitation murder and looting, insult to the Army and offensive words in parliamentary government. "
In 1902 he was hired under a false name in Lens. In October of that year a strike broke out for 8 hours. He opposed the "old" reformist miners' union controlled by Émile Basly. He was again sentenced for "infringement of the freedom to work" and "identity theft".
He was released from prison in 1903 and then became involved in the Jeune Syndicat, edited the newspaper "Le Réveil syndical" and L'Action syndicale. Supporting revolutionary general strike, he also advocated free love following the American anarchist Emma Goldman, and was condemned for immorality (outrage aux bonnes mœurs).
On March 10, 1906, the Courrières mine disaster made 1,101 victims. The strike swept the entire basin and Benoit was arrested while marching with 2,000 strikers on the mayor of Lens.
He was discharged at the end of May, and continued to edit the "action association" with a small printing press.
In 1906 he took part to the Congress of Amiens of the Confédération générale du travail (CGT) trade union with Georges Dumoulin and Pierre Monatte. The anarcho-syndicalist current had undermined the Guesdist minority. The Charter of Amiens set the basis for the French trade-unionist movement, adopting a stance of independence between political parties and trade unions. This charter is still claimed by the CGT and other unions.
In August 1907, he took part in the International Anarchist Congress of Amsterdam. The congress focused on the relationship between unionism and anarchism. He witnessed a strong opposition between Monate and Errico Malatesta: Monate defended revolutionary trade unionism, on one hand, while Malatesta, on the other hand, thought unionism could only be reformist.
Shortly before the Congress, he escaped the police following a meeting, which was organized to protest against the arrest of his friend André Lorulot. In January 1912, he was sentenced to a year in prison after escaping from the penal colony, amnestied in July of that year.
In 1914, recorded in the Livret B (an illegal list, by the police, of people tied to the anarchist movement), he was arrested and sent to the military front. In 1916, he was gassed during a German attack. He was then hired as a taxi driver in the Compagnie générale des taxis. He worked at Sébastien Faure's antimilitarist newspaper CQFD, and then in Le Libertaire.
He took part in the 1921 Lille Congress of the CGT, which followed the Tours Congress of the French Section of the Workers' International (SFIO), during which the Socialist Party split following the creation of the Third International, and was shot by a fellow reformist.
In 1925 his health deteriorated and in 1931, his son, Germinal, was killed by the police at the age of 26.
In 1940, poor and ill, he took refuge in Villeneuve-sur-Lot where he died on June 2, 1944.