Abstract: To enable simple and accurate measurement for the flow rate (emission flux) of a chemical substance released from a site to be measured such as a floor surface, ceiling, wall surface, or furniture with no effect of external air (air in the room). [Means for Solution] An opening 14 for taking in a chemical substance released from an inspection object (13) into the casing (12) is formed to the bottom surface (12a) of a hollow casing (12) to be bonded to the inspection object (13), a test specimen (15) that takes place color change reaction with the chemical substance under a humid circumstance is disposed to the inner surface of the casing (12) being opposed to the opening (14), and a transparent observing section (12a) is formed to the casing (12) for observing the color change of the test specimen (15) from the outside while bonding the inspection object (13) as it is.