An optical probe for irradiating light onto a subject includes an optical path control unit configured to receive light from outside the optical probe, and change a path of the light within the optical probe; an optical path length control element configured to receive the light having the changed path from the optical path control unit, and change an optical path length of the light as the optical path control unit changes the path of the light; and an optical output unit configured to receive the light having the changed optical path length from the optical path length control element, and output the light.