A bearing retainer having a body formed of steel has a nitride layer on the body surface. The average particle diameter of a nitride contained in the nitride layer is not more than 1 .mu.m. The surface of the retainer is subjected to fluoriding treatment, and is then subjected to nitriding treatment. The above-mentioned oxide is removed by replacing an oxide on the surface of the retainer with a metal fluoride film by the fluoriding treatment. In the nitriding treatment, a gaseous mixture of gas for nitriding, for example, ammonia gas and hydrogen gas for removing the metal fluoride film is brought into contact with the surface of the retainer. A precise and uniform nitride layer is obtained in a state where the oxide is reliably removed from the surface of the retainer.