Noninvasive living body measuring apparatuses are described, a representative one of which includes: (a) a light source unit for irradiating a measurement region of a living body; (b) a light-receiving unit for detecting optical information from an irradiated measurement region; (c) a first holding unit for holding the light source unit and the light-receiving unit; (d) a second holding unit for holding the first holding unit so as to be movable; and (e) a mounting unit for mounting the second holding unit onto a living body.