Several studies relating to the separation and estimation of L-ascorbic acid and erythorbic acid were reported about the method using acetonitrile system and the method using methylethyl ketone system. The authors scrutinized these two methods for the purpose of separation and estimation of the both acids in foods and confirmed that the method using methylethyl ketone system was excellent. At the same time, it was found that some part of the both acids was oxidized in process of paper chromatography. Therefore, in order to estimate exactly the both acids, it was necessary to make the curve of survival ratio in process of paper chromatography and amend detection ratio. In case of using methylethyl ketone system for the separation and estimation of the both acids added to several foods and amending detection ratio, detective error was about 10% for the both acids.