A laser crystallization apparatus, which enables an observation of a high
spatial resolution with several .mu.m and a high temporal resolution with
several nanoseconds, comprising a crystallization optical system to
irradiate a laser light to a thin film provided on a substrate and to
melt and crystallize the thin film, the laser crystallization apparatus
comprises an illumination light source disposed out of an optical path of
the laser light and emitting an illumination light for observation to
illuminate the thin film, an illumination optical system comprising an
annular optical element which has the optical path of the laser light in
the center and which leads the illumination light from the illumination
light source to the thin film along the optical path, and an observation
optical system which displays a magnified image of the substrate
including the thin film.