A line glower usable in water, rain, snow or in a place where an explosion may possibly take place, and adapted to work with a small power to emit light from the lateral side thereof. It comprises a light transmission tube including a transparent core and a clad having a smaller refractive index than the core; a water-proof light source disposed at at least one axial end of the light transmission tube; and a drive unit to turn on and off the light source; the light emitted from the light source and incident upon an end of the light transmission tube being let to go out from a lateral side of the tube.