Leonard J. Mills, 64 a retired Army major and college professor, died Wednesday at Fairfax Hospital after an apparent heart attack.

Born in New York City, he earned a bachelor's degree from the University of Virginia, a master's degree from Columbia University and two law degrees from Brookyln University Law School.

He worked in the New York City department of welfare from 1938 through 1941 and again for a short time in 1948. During World War II, he served in this country and Japan.

Dr. Mills rejoined the Army in 1948 attaining the rank of major, and worked in the Army's civil affairs office. He taught political science and civil administration to foreign government officials.

He saw tours of duty in Japan in the early 1950s. Korea in the mid 1950s, South Vietnam in the early 1960s and the Dominican Republic in the mid-1960s, before retiring in 1965.

Dr. Mills then joined the faculty of Northern Virginia Community College as a professor of government. He later became assistant division chairman for government and economics and chairman of the social science division. He also served as student ombudsman and on the Faculty Senate. An enthusiastic card player, he also sponsored the bridge club.

He is survived by his wife, Bertha, of the home in Alexandria: two daughters, Nancy Fredericka Mills, of Boston, and Harrianne Mills, of Atherton. Calif.; a son, Eugene O., of Charlottesville, Va., a sister, Miriam Mann, of Denver, and a brother, Raymond, of Flushing N.Y.

The family suggests that expressions of sympathy may take the form of contributions to the Leonard J. Mills Lecture Series of Northern Virginia Community College.