A socket includes a housing having a first housing portion and a second housing portion attachable to the first housing portion to cover the first housing portion, a starter transformer and accommodated inside the housing, a central terminal coupled to the starter transformer and disposed inside the housing such that, when the discharge lamp is attached to the socket, a central electrode of the discharge lamp contacts the central terminal. The first housing portion has a base, and a first wall portion extending from the base in a direction in which the discharge lamp is attached to the socket. The second housing portion has a second wall portion which, when the first and second housing portions are attached together, overlaps with the first wall portion such that the first and second wall portions surround the central terminal on an inner side of a peripheral edge of the base.