As a chemical engineer, he was a researcher at the Conservatoire national des arts et métiers and was an assistant to Frédéric Joliot-Curie.
He was active in the underground Communist Party of Poland (KPP) until his arrest in 1934, serving as a secretary in Silesia, Łódź, Warsaw and Kraków, and as a member of the National Secretariat in 1933.
Finder fled to Moscow when the Germans invaded and directed to the Comintern training school as a leader of the 'initiative group' formed to re-establish the Communist movement in Poland.
He was identified, tortured and shot by the Nazis in the ruins of the Warsaw ghetto as they evacuated and demolished Pawiak in July 1944.
His second wife, Gertruda Finder, was a KPP activist and worked in the Polish security apparatus after the war.