A lamp socket, which includes a socket body to hold the bulb, a socket cap fastened to the socket body to hold down the electric wire and having two hooked bottom retaining rods inserted through holes on a socket body and hooked on the ring contact of the bulb when the bulb is plugged into the socket body, a gasket and two spaced water sealing rubbers to seal the socket body against water, a center contact metal plate and a side contact metal plate mounted within the socket body for connection with the tip and ring contacts of the bulb, a deformable intermediate contact metal spring to connect the ring contact of the lamp bulb to the side contact metal plate. The center contact metal plate can be turned through about 90.degree. angle per step and moved from one conductor of the electric wire to another thereof to make a different contact.