To efficiently release heat generated by a semiconductor light emitting device. This object is achieved by a light source module including a circuit board having a surface on which a semiconductor light emitting device is mounted and adapted to be placed on a mounting base of a light source holding member, and a power feeding attachment to supply power to the semiconductor light emitting device, the circuit board including a board part on which the semiconductor light emitting device is mounted, and a conductive circuit formed on a surface of the board part and having a pair of terminal parts and a light source connection part to connect the pair of terminal parts and the semiconductor light emitting device, the power feeding attachment including an electrically-insulating portion formed of an electrically-insulating material having higher thermal conductivity than the board part, and an conductive portion embedded in the electrically-insulating portion except a portion thereof, the power feeding attachment being adapted to be attached to the light source holding member such that the electrically-insulating portion presses at least a portion of the circuit board against the mounting base.