A laser apparatus may include a beam splitter configured to split a pulse laser beam into a first beam path and a second beam path, an optical sensor provided in the first beam path, an amplifier including an amplification region provided in the second beam path and being configured to amplify and emit the pulse laser beam incident thereon along the second beam path, a wavefront controller provided in the second beam path between the beam splitter and the amplifier, and a processor configured to receive an output signal from the optical sensor and transmit a control signal to the wavefront controller.