The tubular lamp device contains a passive and transparent lamp tube whose two ends are plugged into a pair of socket members, respectively. The lamp tube has an axial strip along the circumference coated with a reflective film. The socket member contains a tubular element which receives an end of the lamp tube. Inside the tubular element, a LED element is housed in a hole of a solid lens element which directs the light beams of the LED element towards the lamp tube. The light beams are then reflected by the reflective film to create a large area of illumination as the light beams propagate through the lamp tube.