Disclosed is a probe equipped with an optical system that, in order to observe radiated light emitted from a location to be observed on biological tissue, irradiates the location to be observed with irradiation light and receives the radiated light emitted from the location to be observed, and an imaging device that images a surface image of the location to be observed, wherein the aforementioned imaging device (9) is disposed on the aforementioned optical system (5, 6, 7, 8) on the end of said probe, an axis (X) extending in the lengthwise direction of said probe is set as the rotating axis, and the incidence direction (L2) to said probe of the aforementioned received radiated light and the direction of the visual field (Y) of the aforementioned imaging device are rotated by fixing a relative angle around the rotating axis (X). The aforementioned relative angle is fixed by mounting, on the unit, an optical element (a mirror (8)) and the aforementioned imaging device (a camera (9)), which determine the incidence direction of the aforementioned received radiated light to said probe.
