Provided is an optical scanning unit including: an optical fiber； an actuator； a reducing part； a detection part； and a controller. The optical fiber oscillates the emitting end, to thereby scan the object. The actuator oscillates the emitting end. The reducing part reduces the transmission of light emitted from the emitting end. The detection part detects light at the object when light is irradiated onto the object. The controller forms an image, based on light detected by the detection part and the state of oscillation of the optical fiber. The controller calculates the eccentricity in the image thus formed, based on a position where the received amount of light is reduced and the center position of the image.
