Karl Michael Kunz , 64, an attorney with the Department of Justice for 32 years, died Tuesday at Georgetown University Hospital. He had a heart ailment.

Mr. Kunz joined the Justice Department Antitrust Division in 1947. In 1951, he transferred to the Emergency Planning Office, where he was an employment policy officer and a member of the mobilization plans group. He later returned to the antitrust division and was working there at the time of his death.

He was born in Newport, R.I., and graduated from Providence College in Rhode Island. He earned a bachelor's and a master's degree in law from Georgetown University.

During World War II, he served as an Army Cryptography instructor.

Mr. Kunz was active for more than 20 years in the Rhode Island State Society, which he helped found in the 1950s.

He lived in Washington and attended Our Lady of Victory Catholic Church, where he was an usher, a member of the parish council and a past president of the Holy Name Society.

Survivors include his wife, Margaret, of the home; four sons, Karl M. Jr., of San Luis Obispo, Calif., Kevin B., of the Panama Canal Zone, Paul G., of Silver Spring, and Christopher J., of Wheeling, W. Va; two daughters Mary Margaret, of Fort Collins, Colo., and Catherine Ann, of New York City; one brother, Gustave, and three sisters, Natalie Mello, Louise Baker, and Genevieve Munafo, all of Newport, R.I.

The family suggests that expressions of sympathy be in the form of contributions to the scholarship fund at Our Lady of Victory Church in Washington. CAPTION: Picture,KARL MICHAEL KUNZ