Auto focusing system to find optimized focal position of laser beam used for material process has been investigated by using fiber confocal method. Wavelength of laser diode (LD) and diameter of single-mode fiber are 780nm and $5.3{mu}m$, respectively. Intensity distributions of beam reflected from the surface of mirror and silicon bare wafer have been observed in a gaussian form. Experimental results show that focal position obtained by LD is shifted from one observed from surface scribed by laser about $80{mu}m$. It is due to the difference of wavelength and each divergence of between LD and laser used for material process. It is confirmed that auto focusing control system through position calibration has operated steadily.