Test device and cartridge

A test device that is used for an immunochromatographic test using an immunochromatographic method, the test device comprising:

• a loading portion into which a cartridge is loaded, the cartridge having a strip that is provided with a test region whose color development state changes depending on whether or not a sample includes a test substance and having a case in which the strip is accommodated and in which an observation window for observing the test region from an outside is formed in a surface;
• an illumination unit having an emission end portion through which illumination light for illuminating the test region is emitted and which is disposed at a position separated from the observation window on an outer surface of the case;
• and
• a detection unit that is disposed at a position facing the observation window on a surface side of the case and that optically detects the color development state of the test region irradiated with the illumination light,
• wherein the illumination unit is configured such that the illumination light is transmitted from the outer surface of the case to an inside of the case, reaches the test region while being diffuse-reflected by an inner surface of the case, and illuminates the test region from the surface side.