To make it possible to efficiently radiate light onto a test paper even in the case where a light source with small quantity of light is used, as well as adjust the diameter and illuminance distribution of an irradiation spot projected onto the test paper. A device has a mounting portion on which a tip (100) is mounted, a light source (80a) for emitting light having a predetermined wavelength, and a light-receiving element (44) for receiving the light reflected from a test paper (107). The device further includes a condensing lens (53) on which the light emitted from the light source 80a is incident and which condenses the light on the test paper (107), and a light-path block (26). The light-path block (26) is provided with a diaphram portion arranged between the condensing lens (53) and the light source (80a), at the position of the photographic subject (object) of the condensing lens (53).
