<p>An apparatus for detecting the velocity information of an object comprises the irradiation optical system for performing the irradiation of beam to the predetermined position on an object to be measured; the photodetector for detecting the light from the irradiated object by the irradiation optical system, the velocity information being obtained by the detection; the detector for detecting the irradiating state for detecting the deviation of the irradiating position of the beam on the object to be measured; and the adjuster for adjusting the irradiating state of the beam on the object based on the detection result of the detector for detecting the irradiating state. With such constituents as above, the apparatus is capable of dealing with the fluctuation of the lightning to obtain a high-precision detection of the velocity information at a high speed. <IMAGE></p>
