A laser apparatus includes: a plurality of envelope blocks each provided with an optical element and a first temperature sensor and covering part of a laser beam path, the optical element being disposed on the laser beam path, the first temperature sensor being configured to measure a first temperature of gas at a position away from the optical element; an envelope body including the envelope blocks and covering the laser beam path; and a control unit connected with each first temperature sensor and configured to specify an envelope block at which increase of the first temperature is measured in the envelope body as an envelope block at which anomaly is occurring.