A light source module includes a substrate, a first covering layer, a second covering layer, a luminous layer and a supporting base. The luminous layer is arranged between the first covering layer and the second covering layer. The luminous layer emits a light beam in response to a first current flowing through the first covering layer and a second current flowing through the second covering layer. The light beam is projected to surroundings through the substrate. The supporting base is electrically connected with the first covering layer and the second covering layer. The supporting base includes a circuit board and a passivation layer. When a portion of the light beam projected to the supporting base is reflected by the passivation layer, the portion of the light beam is projected to the surroundings through the substrate.