To provide a lid member for an IC socket which can simply and surely connect connection terminals of IC and to provide an IC socket assembly having the same.

The IC socket comprises terminals, a flat plate-shaped housing member 10 having a plurality of housing holes housing the terminals, a flat plate-shaped slide member 20 held by the housing member so as to be able to slide on one plate surface of the housing member. A lid member 40 mounted to the slide member 20, for the IC socket which is made possible to slide between a stand-by position where a connector of the IC, penetrating through a connection hole by zero insertion force or low insertion force, faces the terminals, and a connecting position where the IC contacts with the terminals with pressure, has a locking member 42, preventing the slide member 20 from sliding movement to the connecting position by locking with the slide member 20 and the housing 10, by being mounted to the slide member 20 when the slide member 20 stays at the stand-by position.