Rudolph J. Faupl, 73, a retired union official and former delegate to the International Labor Organization, died Thursday at his home in Fairfield, Calif., after a heart attack.

Mr. Faupl was a worker delegate to the International Labor Organization, a United Nations agency, from 1957 to 1972. From 1951 until his retirement in 1973, he was the liaison officer of the International Association of Machinists and Aerospace Workers (IAM) with other American labor unions and also with the ILO.

He made his home in Arlington for 20 years before moving to California in 1975.

Mr. Faupl was a born in Budapest and reared in Milwaukee. He joined the Fabricated Metalworkers Union as a machinist in Milwaukee in 1925. Later in the 1920s, he joined what became the IAM. He became an organizer with the Wisconsin State Federation of Labor in 1936.

During World War II, he was a labor member of the Sixth Regional War Labor Board in Chicago. He returned to the machinists' union after the war and moved here from Milwaukee in 1955.

Survivors include his wife, Viola, of Fairfield; two daughters, Marilyn Pfahl, also of Fairfield, and Joanne Redington of Jackson, N.J.; seven grandchildren and one great-grandchild.