A single socket containing two lamps toward opposite directions includes a longitudinal lateral opening, an introrse plate and a pair of the first wire grooves in the center for disposing a pair of electric wires, a pair of flat surfaces each having a transverse retaining slot and a retaining edge, a pair of separated slits and a single slit in two sides of the flat surfaces for respectively disposing a pair tipped contact plates and a common contact plate and a pair of first retaining recesses through the peripheral walls adjacent the upper and lower rims, a cover closing the lateral opening having a pair of second wire grooves, two pairs of the hooked plates and a pair of second retaining recesses in inner side respectively engaged with first wire grooves, the transverse retaining slots and the retaining edges of the opening, a pair of lamps inserted into the upper and lower rims of the socket each having a pair of lead-in wires engaged with the contact plates respectively and a pair of retaining rings respectively sleeved on the outer periphery adjacent the upper and lower rims of the socket.