A backlight module includes a back plate, replaceable light source sets, external electrode lamps, and a fastening device. Each replaceable light source set is disposed on the back plate and has an electrically conductive strip. The external electrode lamps are disposed on one of the replaceable light source sets and each has an external electrode electrically connected with the electrically conductive strip. The fastening device is used for fastening the replaceable light source sets and comprises an electrically conductive element electrically connected with the electrically conductive strips.