Total organic carbon analyzer

[PROBLEMS] To use in a carbon dioxide separation part a gas-permeable membrane with which high-speed determination can be maintained and to diminish the influence of interfering ingredients. [MEANS FOR SOLVING PROBLEMS] An analyzer is provided which comprises: an organic-substance oxidation part where organic substances contained in a sample water supplied are oxidized into carbon dioxide; a carbon dioxide separation part where the carbon dioxide contained in the sample water which has passed through the organic-substance oxidation part is caused to permeate and move to a test water; and a conductivity measurement part where the conductivity of the test water from the carbon dioxide separation part is measured. The carbon dioxide separation part includes: a sample water channel where the sample water which has passed through the organic-substance oxidation part is caused to flow; an intermediate water channel where an intermediate water is caused to flow, the intermediate water having a pH value which is higher than that of the sample water flowing through the sample water channel and is in a neutral region; and a test water channel where the test water comprising deionized water is caused to flow. The sample water channel is in contact with the intermediate water channel through a gas-permeable membrane, and the intermediate water channel is in contact with the test water channel through a gas-permeable membrane.