Abstract: Provided are a variable pulse width flat-top laser device and an operation method therefor. A variable pulse width flat-top laser device includes a light source unit including first and second laser light sources driven at different times to respectively emit pulse-type first and second laser beams, a beam shaping unit configured to shape the first and second laser beams emitted from the light source unit into flat-top laser beams, a combination/split unit located between the light source unit and the beam shaping unit, and including a first beam combination/split unit configured to combine optical paths of the first and second laser beams and split a combined optical path into at least two optical paths so that the split at least two optical paths are directed to different regions of an incident surface of the beam shaping unit, and an imaging optical system configured to time-sequentially overlay the flat-top laser beams shaped by the beam shaping unit on a target object to form an image.