An optical stimulation probe has a probe body inserted into a subject, an electrode formed on the probe body and collecting a response signal from the subject, a light irradiator attached to the probe body and irradiating an optical signal and a reflecting surface formed on the probe body on the path of the optical signal. The reflecting surface changes the course of the optical signal irradiated from the light irradiator to the direction where the electrode faces by reflecting the optical signal. The electrode may be formed on a side portion of the probe body such that it faces a direction perpendicular to a length direction of the probe body, and the optical signal reflected by the reflecting surface may travel along a direction perpendicular to the length direction of the probe body, such that the direction where the electrode faces and the direction along which the reflected optical signal travels are parallel to each other.