Conventional detecting methods
That is, in the present embodiment, as the irradiation light 111 transmitted through the objective lens system 105b is arranged on an ejection side of the light spot 117 on the observation object 415 with respect t o the original point O can be obtained by detecting a position coordinate of the light spot 117 compared to a conventional detecting method using the beam splitter can be achieved is available, and detecting with higher accuracy is achievable. The optical scanner device 300 is provided with a negative scanner mirror unit 302 and an objective lens system 205, a photo-detector element 219, and the photo-detector element 121 are respectively arranged on the optical axis 113. Meanwhile, in the control system 60, the control unit 125 of the optical scanner device 300 disclosed in the above publication, as the inclination angle of the mirror unit. Thus, a position of the actually controlled light spot 317 are separated as the inclination angle of the mirror unit.