A laser processing apparatus including a detecting unit. The detecting unit includes a white light source for emitting white light, a focusing lens for focusing the white light to the workpiece, a first optical fiber for guiding the white light emitted from the white light source to the focusing lens, a detector for detecting the intensity of reflected light from the workpiece, and a second optical fiber for guiding the reflected light to the detector. Accordingly, the white light to be focused to the workpiece can be easily handled and only a wavelength component focused on the workpiece can be stably propagated.