A gas concentration prediction method which includes: step 1 of exposing a gas to a specimen A which contains a liquid containing a compound, and to a specimen B which includes a liquid containing the compound in a concentration lower than the concentration of the compound in the specimen A, under the same conditions X, and step 2 of measuring a gas concentration a in the specimen A obtained in step 1, and a gas concentration b in the specimen B obtained in step 1, to obtain a coefficient α by calculating the relationship between a and b based on the calculation equation α=a/b.