Gertrude Johanna (Jo) Banfield, 64, a retired office manager, died of leukemia Thursday at Johns Hopkins University Hospital in Baltimore.

From 1959 until her retirement in 1975, she was office manager and treasurer of Robert F. Hoff, Inc., a plumbing firm in Edmonston.

Born in Bay City, Mich., Mrs. Banfield attended Michigan State University. She moved to Baltimore in 1937 to work for the newly established Social Security Board.

A year later she became secretary to the head of the old Children's Bureau in the Labor Department, remaining there until resigning in 1944 to raise her family.

A member of Holy Redeemer Catholic Parish in College Park, Mrs. Banfield was cofounder of the Altar Society there. She was active in the movement to establish free kindergartens in Prince George's County.

She is survived by her husband, William L., of the home in College Park; a sone, Dr. William J., of Cambridge, Md.; three daughters, Mary Jo Dorough, of Bethesda, Kathleen Hammond, of Huntington, Md., and Teresa Ann, of North Carolina; two sisters, Clara Klinski, of Silver Spring, and Helen Forbes, of Warren, Mich.; two brothers, Chester Klinski, also of Warren, and Edward Klinke, of Royal Oak, Mich., and seven grand-children.