An LED mounting seat includes a main body having a supporting surface that abuts against a light emitting portion of an LED, a connecting end that is connected to a circuit board, and a side surface that interconnects the supporting surface and the connecting end. The side surface is formed with a pair of lateral grooves. Each of the lateral grooves is defined by a groove-defining surface that has an abutting surface portion facing an opening of the corresponding one of the lateral grooves. The LED has two leads extending respectively through the lateral grooves and abutting respectively against the abutting surface portions of the groove-defining surfaces.