Provided are a measurement probe and bio-optical measurement system making it possible to precisely irradiate living tissue with illumination light without diminishing yield. A measurement probe (3) provided with: a fiber bundle (300) constituted of a plurality of optical fibers (315) bundled together an optical element (34) for maintaining a constant distance between a biological tissue and an end surface of the fiber bundle (300), the optical element (34) being provided to the distal end section of the fiber bundle (300) and a connector section (31) for housing the proximal end section of the fiber bundle (300), the connector section (31) being detachably connected to a bio-optical measurement device for supplying an illumination light to the biological tissue and running optical measurements wherein proximal end sections (315a) of those optical fibers (315) where an irradiation region of the optical fibers (315) through which the illumination light emitted by the bio-optical measurement device is relayed and emitted, the irradiation region being at the distal end of the optical element (34), is smaller than the surface area of the distal end are arranged at a position facing the position of emission of the illumination light in the bio-optical measurement device.Linvention concerne une sonde de mesure et un système de mesure bio-optique rendant possible dirradier de façon précise un tissu vivant avec une lumière déclairage sans diminuer le rendement. Linvention concerne une sonde de mesure (3) comportant : un faisceau de fibres (300) constitué dune pluralité de fibres optiques (315) regroupées ensemble en faisceau un élément optique (34) pour le maintien dune distance constante entre un tissu biologique et une surface dextrémité du faisceau de fibres (300), lélément optique (34) étant disposé à la section dextrémité distale du faisceau de fibres (300) et une section de connexion (31) pour recevoir la section dextrémité proximale du faisceau de fibres (300), la
