PROBLEM TO BE SOLVED: To provide a hydrogen peroxide gas detection indicator that allows discoloration to be more surely viewed even under a different environment in relative moisture.SOLUTION: The present invention relates to an ink composition for detection of hydrogen peroxide gas containing (1) at least one of ketone-based resin and (2) at least one of a methine-based dye. That is, the ink composition according to the present invention and an indicator by the ink composition employ a combination of (1) at least the one of the ketone-based resin and (2)at least the one of the methine-based dye, and then, when a discoloration layer is formed, using the combination thereof, an effect can be obtained that allows the discoloration in accordance with hydrogen peroxide gas concentration and the like to be viewed without being affected by relative moisture.
