A laser processing apparatus, in accordance with at least one exemplary embodiment, is configured to contemporaneously perform the functions of observing a surface of a substrate and concentrating laser light to a given position inside the substrate. The laser processing apparatus can include an optical system having an afocal optical subsystem configured to concentrate laser light inside the substrate. Adjustment of the position of a laser light concentrating point can be achieved independent of adjustment of a focal point by the automatic focusing mechanism to observe the surface of the substrate irradiated with laser light.