It has been reported that lubricants are degraded at the head/disk sliding interface of thin film magnetic media as a result of the decomposition of the molecules. The lubricant degradation is a serious problem for the magnetic recording apparatus since it leads to the wear of important magnetic recording layer. One of the possible reactions that result in the decomposition of the lubricant molecules is caused by the electrons emitted from the wearing overcoat surface of the thin film magnetic disk. However, the electron emission mechanism of the carbon films has not yet been investigated in detail so far. This paper discribes the electron emission characteristic of a frictional system of Al₂0₃ ball sliding on amorphous carbon(a-C) and hydrogenated carbon(a-C:H) films which are used as overcoat films for the thin film magnetic disk. The characteristic of the electron emission is discussed with the wear mechanism of the carbon films.