The erosion of carbon deposition layers by oxygen exposure and the desorpstion of hydrogen retained in the layers were investigated experimentally. Carbon deposition layers were formed by a sputtering method using hydrogen RF plasma. The layers were exposed to an argon gas with oxygen of 1013 Pa in the temperature range of 200-400°C. The erosion reaction progressed quickly within 10 minutes and then decelerated rapidly. The measurement of the outlet concentration revealed that most of the layer was eroded not as carbon monoxide and carbon dioxide but as soot. Additionally, it was estimated that the soot was released from the carbon deposition layer with a large amount of hydrogen.