A laser apparatus according to an aspect of the present disclosure includes: a master oscillator; at least one amplifier disposed on an optical path of a first pulse laser beam output from the master oscillator; a sensor disposed on an optical path of a second pulse laser beam output from the at least one amplifier; and a laser controller. The laser controller causes the laser apparatus to perform burst oscillation based on a burst signal from an external device, and performs processing of controlling a beam parameter based on a sensor output signal obtained from the sensor in a burst duration, and processing of detecting self-oscillation light from the amplifier based on a sensor output signal obtained from the sensor in a burst stop duration.