To provide an exposure system which can stably operate focus servo control by using laser light for exposure and makes high density recording possible.

The exposure system is equipped with at least an objective lens 8 to condense laser light emitting from a laser light source 4 to a photoresist applied on a plate D to be exposed; and a focus servo controlling means 12 to control the focus by the reflected light from the photoresist. The system is also equipped with a main controlling means 13 to control the focus servo controlling means to change the position of the objective lens in such a manner that the laser light is rightly focused on the photoresist in an exposure period and that the laser light is defocused within the focus control range and does not expose the photoresist in a non-exposing period.