A laser machining device for cutting or welding a material to be machined by irradiating the material to be machined with laser light, the laser machining device comprising: a surface plate on which the material to be machined is placed; rails arranged along the surface plate; a machining trolley including a saddle mounted on the rails, a garter arranged in a direction perpendicular to the rails and connected to the saddle, a transverse carriage mounted on the garter, and a laser nozzle mounted on the transverse carriage, and configured to cut or weld the material to be machined by irradiating the material to be machined with the laser light through the laser nozzle while allowing the saddle to travel along the rails and the transverse carriage to perform traverse along the garter; and a cover that covers approximately an entire surface of the machining trolley, and includes an upper surface cover body arranged on an upper surface side of the machining trolley, a laser nozzle-side cover body arranged on a laser nozzle side of the machining trolley and having an upper end connected to the upper surface cover body, a garter-side cover body arranged on an opposite side to the laser nozzle of the machining trolley and having an upper end connected to the upper surface cover body, and two side surface cover bodies (14, 15) having an upper end connected to the upper surface cover body and both ends in a width direction connected to the laser nozzle-side cover body and the garter-side cover body, wherein a light-blocking member having flexibility is attached to lower end sides of the laser nozzle-side cover body and the garter-side cover body that configure the cover, the light-blocking member being for preventing leakage of the laser light through gaps between the lower end portions and the upper surface of the surface plate, and characterized in that the light-blocking member is configured from a plurality of sheets having flexibility and a light-blocking property, and being layered and having a slit formed in a different position in every sheet, wherein an upper end of the layered sheets is attached to the lower end side of the laser nozzle-side cover body and the garter-side cover body. a surface plate on which the material to be machined is placed; rails arranged along the surface plate; a machining trolley including a saddle mounted on the rails, a garter arranged in a direction perpendicular to the rails and connected to the saddle, a transverse carriage mounted on the garter, and a laser nozzle mounted on the transverse carriage, and configured to cut or weld the material to be machined by irradiating the material to be machined with the laser light through the laser nozzle while allowing the saddle to travel along the rails and the transverse carriage to perform traverse along the garter; and a cover that covers approximately an entire surface of the machining trolley, and includes an upper surface cover body arranged on an upper surface side of the machining trolley, a laser nozzle-side cover body arranged on a laser nozzle side of the machining trolley and having an upper end connected to the upper surface cover body, a garter-side cover body arranged on an opposite side to the laser nozzle of the machining trolley and having an upper end connected to the upper surface cover body, and two side surface cover bodies (14, 15) having an upper end connected to the upper surface cover body and both ends in a width direction connected to the laser nozzle-side cover body and the garter-side cover body, wherein a light-blocking member having flexibility is attached to lower end sides of the laser nozzle-side cover body and the garter-side cover body that configure the cover, the light-blocking member being for preventing leakage of the laser light through gaps between the lower end portions and the upper surface of the surface plate, and characterized in that the light-blocking member is configured from a plurality of sheets having flexibility and a light-blocking property, and being layered and having a slit formed in a different position in every sheet, wherein an upper end of the layered sheets is attached to the lower end side of the laser nozzle-side cover body and the garter-side cover body.