A laser cutting device according to one embodiment comprises a laser generating unit, an optical unit, a worktable and a suction unit, wherein the laser generating unit generates a laser beam. The optical unit is fixed in an advancing path of the laser beam. The worktable is used for placing a cutting object. Furthermore the suction unit is fixed between the optical unit and the worktable and sucks smoke. The suction unit comprises a body and a pipe which is connected with the body. Furthermore the body comprises an outer box and an inner cup which is fixed in the outer box in a separable manner.