To provide a sampling clock generating device capable of removing deterioration in linearity due to irregularity of characteristics such as a distortion, etc., of an optical system and precisely sampling by giving a mirror position detection optical system of a scanner used for scanning a confocal optical characteristic equivalent to an objective optical system.

A laser beam from a laser light source 21 is led to the scanner 22, and is reflected by a mirror surface to be converged on the mirror position detecting scale 24 of the scanner 22 by a lens 23. A sampling clock is generated from a comparator 30 through an amplifier 29 from a photodetector 28 according to the movement of the laser beam on the scale 24 by the operation of the scanner 22. On the other hand, since observation light from the laser light source 6 emitted to a specimen 11 by the objective optical system is synchronized with the movement of the laser beam on the scale 24, the surface information of the specimen 11 is obtained by sampling an image signal from the photodetector 15 by the sampling clock from the comparator 30.