A socket fixed to a heat sink holds a card-type LED module formed by integrating LED elements. The socket (6) includes: a frame structure for holding the LED module (1000) with its light source unit exposed through the frame opening; and a pressing member positioned around the opening for pressing the back surface of the LED module against the heat sink (2122). The socket may include a structure including a lower member (61) placed on a heat sink and an upper frame member (62) holding the LED module with its light source unit (1002) exposed through the frame opening. The upper member supported by the lower member via a hinge can open/close, and includes a pressing unit pressing the LED module set in the open state, against the lower member (61). The lower member (61) includes, in its main part, a lock unit (63) directly or indirectly lock the upper member (62) when the upper member is closed.