Fluorescence from the wall surface locating near is reliably received. A probe (2) for the reception and for irradiating an observation object part of an organism tissue with excitation light after the probe (2) is inserted into a lumen (K) of a body in the axial direction X and detecting the fluorescence resulting from the excitation light is provided with an objective optical system (4) so provided as to be directed toward the end of the probe (2) and a plurality of optical fibers (30b) which is so provided that the end surfaces (300) are directed toward the objective optical system (4) and the optical fibers are in positions set off the optical axis (J) of the objective optical system (4) and which is used for receiving fluorescence traveling through the objective optical system (4) at the end surfaces (300). The positions of the end surfaces (300) of at least the optical fibers (30b), among the optical fibers (30b), different from one another in the offsets from the optical axis (J) of the objective optical system (4) are different film one another along the optical axis (J) of the objective optical system (4).
