PURPOSE: To obtain information on a body to be inspected at a high speed in a short time by providing a 1st and a 2nd reflection parts which reflect the light reflected by a rotatable mirror and are annularly arranged.

CONSTITUTION: This optical scanning device is equipped with a couple of primary and secondary reflecting devices 2 and 3 which are arranged annularly and concentrically in a gantry 1, a reflection and light receiving unit 4 which is arranged at the center position of the primary reflecting device 1, and a laser unit 5. The center axis of rotation of the reflection and light receiving unit 4 is aligned with the optical axis of output light of the laser unit 5. The laser light 5a emitted by the laser unit 5 is radially refracted by the mirror of a reflector light receiving unit 20 and reflected by the mirrors 12 and 14 of the primary and secondary reflecting devices 2 and 3 to become parallel light, which is made incident on the body 6 to be inspected; and the transmitted laser beam 5a is reflected by the liquid crystal shutters 15 and 13 of the secondary and primary devices 3 and 2 and made incident on a light receiving part 24, which measures its intensity. This measuring operation is carried on covering a 360° angle while the reflector light receiving unit 20 is rotated.