PURPOSE: An Indoor lighting module of a vehicle is provided to prevent damage to the interior design of a vehicle and to reduce installation costs. CONSTITUTION: A main board(1) is supported to a support body(2) and comprises a constant current board. The constant current board converts applied reference power into output power. A reflective plate(3) is installed under the support body and reflects light. A light guide plate(4) guides the reflected light downward. A light emitting lamp(7) emits light. A cover(8) is coupled to the support body and has a light transmitting window. The light guided from the light guide plate passes through the light transmitting window.