To provide a biological information detector or the like in which the detection accuracy or the measurement accuracy can be increased. A biological information detector includes a light-emitting part (14) for emitting light (R1) directed at a detection site (O) of a test subject a light-receiving part (16) for receiving light (R1) having biological information, the light (R1) being light (R1) emitted by the light-emitting part (14) and reflected at the detection site (O) and a contact part (19) formed from a material that is transparent with respect to a wavelength of light (R1) emitted by the light-emitting part (14), the contact part (19) having a contact surface (19A) that makes contact with the test subject and an opposing surface (19B) disposed opposite the contact surface (19A). The light-emitting part (14) is installed on the opposing surface (19B).
