A laser device includes: a laser resonator for emitting a laser beam; a condenser lens for collecting the laser beam emitted from the laser resonator; an optical fiber for transmitting the laser beam collected by the condenser lens; at least one light sensor opposing a light receiving surface of the condenser lens and outside an optical path of the laser beam, the at least one light sensor detecting an amount of return light from the condenser lens; and a controller for determining a presence of an abnormality when a value of the amount detected by the at least one light sensor is greater than a predetermined maximum threshold.