To support a socket body movably in the forward and backward directions and realize the thinning of a lamp socket by forming, in the socket body, mounting slots perpendicular to the opening direction of a lamp pin mounting opening formed in its front face, and fitting a mounting spring part of a mounting plate to the slots.

A lamp pin mounting opening 4 is opened in the front face 3 of a generally box-shaped socket body 1, a contact spring 8 corresponding to a lamp pin is arranged in its inside, and a lamp pin insertion slot 6 is continuously formed at a tip part 7. In addition, on both side surfaces 18 of the socket body 1, a pair of mounting pieces 15 are stretched tightly and mounting slots 5 perpendicular to the opening direction of the lamp pin mounting opening 4 are formed. The socket body 1 is arranged in a generally I-shaped hole 19a of a mounting plate 2, and a mounting spring part 19 having a spring elasticity of the mounting plate 2 is fitted to the mounting slots 5. Thereby, a thin lamp socket mounting structure having a thickness of only the sum of the thickness of the socket body 1 and the stroke length of elastic deformation while it is mounted is provided.