A laser processing device for processing a workpiece is provided, including a laser emitter, a lens module, a driving module, a camera module, and a processing unit. The lens module has a first lens and a second lens, wherein the laser emitter emits a laser beam through the first and second lenses to the workpiece. The driving module drives the first lens to move relative to the second lens. The camera module captures an image of the workpiece. The processing unit is electrically connected to the camera module and the driving module, wherein the camera module transmits an image signal to the processing unit according to the image of the workpiece, and the processing unit transmits a driving signal to the driving module according to the image signal, driving the first lens to move relative to the second lens. A method for processing a workpiece is also provided.