Disclosed is a laser device. The laser device includes a pulse generator which irradiates a laser beam between a high reflector mirror and an output coupler mirror to amplify and resonate the laser beam, a pulse output section which receives a laser beam pulse amplified and resonated through the output coupler mirror to output the laser beam pulse, and a Q switch which moves backward or forward in a direction perpendicular to a path of the laser beam formed between the pulse generator and the high reflector mirror. The output coupler mirror includes first and second mirrors provided on a base plate. Positions of the first and second mirrors are selectively changed as the Q switch moves backward or forward.