A lighting device for a vehicle lamp has a base, a substrate, a conducting rib and an LED module. The substrate is mounted in the base. The conducting rib is perpendicularly mounted on the base and has a first heat-dissipating surface and a second heat-dissipating surface opposite to the first heat-dissipating surface. The conducting rib provides two heat dissipating paths to increase the heat dissipating efficiency. The LED module is mounted on a distal end of the conducting rib and extends out of the base, and the LED module is electrically connected to the substrate. The LED module extends out of the base to accurately correspond to a reflection space around a lamp seat and improve the light-homogenizing effect of the vehicle lamp.