A dental caries diagnosis device comprising a light source which is configured to emit examination light (R) and a light receiving unit (4f) which is configured to receive the examination light (R) with which a tooth has been irradiated includes: a head-side casing (4a1) which is inserted into a mouth in a contactless manner with respect to a tooth or a gum and which projects the examination light (R) toward a tooth； and a filter (4e) which is disposed in front of the light receiving unit (4f) and which is configured to remove a noise component from the received light, wherein the light receiving unit (4f) is configured to receive the examination light (R) which has been transmitted through the tooth.
