The device relates to a device for marking, during nighttime riding through a transport vehicle such as bicycles, two-wheeled vehicles, electric wheelchairs, etc., a rider's temporary dedicated road lines by laser-emitting means mounted at the rear side of the transport vehicle, thereby ensuring the safety of the rider of the transport vehicle. The device includes: laser-emitting modules adapted to form luminous lines spaced apart from each other by a predetermined distance on the road beside or behind the transport vehicle; a power supply module adapted to supply power to the laser-emitting modules; an external housing adapted to accommodate the laser-emitting modules thereinto; and a fixing module adapted to fix the external housing to the transport vehicle.