A breath test device provided with a main body part 20 to which a gas sensor for measuring an infrared absorptivity of a testee's breathing gas is communicably connected thereto, wherein the main body part 20 includes: a measuring part 21 which measures the concentration of carbon dioxide contained in the testee's exhaled breath based on the measurement result by the gas sensor for a period from the start to the end of a preset plurality of breathings which is taken as a measurement unit； a storage part 24 which stores the measurement result by the measuring part 21 at least for the measurement unit； a display part 25 which displays the measurement result by the measuring part 21 on a screen； and an screen control part 26 forming, as an image that the display part 25 is controlled to display, a display image including all of capnogram waveforms arranged side-by-side on the screen based on the contents stored in the storage part 24, each capnogram waveform representing time-dependent change in the carbon dioxide concentration for the measurement unit.
