A biological information detector including a light-emitting part for emitting a light directed at a detection site of a test subject, a light-receiving part for receiving a light having biological information, the light produced by the light emitted by the light-emitting part being reflected at the detection site, a reflecting part for reflecting the light emitted by the light-emitting part or the light having biological information, a protecting part, having a transparent surface in contact with the test subject, for protecting the light-emitting part or the light-receiving part, and a substrate held between the reflecting part and the protecting part, the light-emitting part being positioned on a side of the substrate towards one of either the reflecting part or the protecting part, and the light-receiving part being positioned on a side of the substrate towards another of either the reflecting part or the protecting part.
