John B. Mealy, 72, an administrative law judge at the Department of Labor who retired in 1970 after 40 years of government service, died of liver failure Monday at Holy Cross Hospital in Silver Spring.

Mr. Mealy, who was born in Washington, graduated from Gonzaga College High School, earned a law degree at Columbus University and was admitted to the D.C. Bar. In the course of his government career, which began in 1930, he worked for the departments of Labor, Agriculture, Commerce and Health, Education and Welfare, the Veterans Administration and the Interstate Commerce Commission.

During his first period at Labor, Mr. Mealy was a public contracts investigator and a supervising attorney. About 1955, he was appointed an administrative law judge at HEW. He later transferred to the ICC, where he worked in the same capacity. In the early 1970s, he returned to Labor as an administrative law judge.

Mr. Mealy, who lived in Silver Spring, was a member of the parish and a lector of St. Michael the Archangel Catholic Church. He was a member and past president of its Men's Club and coached youngsters in basketball, touch football and baseball. He also was active in the Boy Scouts at the parish.

Survivors include his wife, Sarah Crawley Mealy of Silver Spring; three sons, Hugh M., of Mitchellville, J. Burke, of Gaithersburg, and Michael O., of Alexandria; one brother, Joseph F., of Palm Beach Gardens, Fla., and four grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to the Children's Hospital National Medical Center, 111 Michigan Ave. NW.