A laser crystallization apparatus according to an embodiment includes a light source unit irradiating a laser beam; and an optical unit to which the laser beam is incident, wherein the optical unit includes a first portion and a second portion bonded to each other on a bonded surface, and a first width of the first portion and a second width of the second portion are the same as each other on the bonded surface based on a direction parallel to the incident direction of the laser beam.