A laser apparatus includes: a first vacuum chamber, wherein machining is performed on a target substrate in the first vacuum chamber; a laser facing the first vacuum chamber; a carrier disposed in the first vacuum chamber, wherein the target substrate is seated on the carrier; a chamber window disposed in one surface of the first vacuum chamber, wherein a laser beam emitted by the laser passes through the chamber window; a first protection window positioned between the carrier and the chamber window; a second vacuum chamber disposed at a first side of the first vacuum chamber; and a transfer unit configured to transfer the first protection window to the second vacuum chamber.