According to the present invention, dynamic components in living tissue, such as blood flow, are measured without hiding the surface of the living tissue. Provided is a blood vessel determination system provided with a medical probe (2), a photo-detection unit, and a processor (6). The medical probe (2) includes: a first transmission path (8) which transmits laser light P for irradiating a living tissue (A) and which outputs the laser light P from an output end (8a) thereof； a second transmission path (9) which receives, at an input end (9a) thereof, scattered light (R) from the living tissue (A) including information about a dynamic component in the living tissue (A), and which transmits the scattered light (R)； and an optical element (10) for causing the laser light (P) output from the output end (8a) to be refracted when the living tissue (A) is to be irradiated therewith, and for causing the scattered light (R) from the living tissue (A) to be condensed when received at the input end, the optical element (10) generally having a positive power. The photo-detection unit detects the scattered light (R) received at the input end (9a). The processor (6) determines the presence or absence of a blood vessel on the basis of the dynamic component information.Selon la présente invention, des composants dynamiques dans un tissu vivant, tels que le débit sanguin sont mesurés sans dissimulation de la surface du tissu vivant. L'invention concerne un système de détermination de vaisseau sanguin équipé d'une sonde médicale (2), d'une unité de photo-détection, et d'un processeur (6). La sonde médicale (2) comporte: un premier trajet de transmission (8) qui transmet de la lumière laser P pour irradier un tissu vivant (A) et qui émet en sortie la lumière laser P à partir d'une extrémité de sortie (8a) de celui-ci； un second trajet de transmission (9) qui reçoit, au niveau d'une extrémité d'entrée (9a) de celui-ci, la lumière diffusée (R) par le tissu vivant (A) comprenant une info
