A socket assembly (1) includes a socket (2) and a vacuum pickup cap (3). The socket includes a base (20), a cover (21) movably assembled upon the base and an actuating rod (22) assembled on both the base and the cover for driving the cover to move in relative to the base. The cover defines a through hole (200) in a center thereof. The vacuum pickup cap includes a flexible bottom plate (31) and a flexible film (32). The flexible bottom plate has a sticky bottom surface (310) adhered to an upper surface of the cover and covering the through hole of the cover. The flexible film has a sticky bottom surface (320) adhered to the flexible bottom plate and a smooth upper surface (321) adapted for being sucked by a vacuum pickup device.