a lower test socket mounted on a tester providing a test signal, and connected to a lower terminal of a lower package to electrically connect the lower package to the tester;

a pusher configured to be able to be moved vertically by receiving a driving force from a driving unit;

an upper test socket mounted on the pusher, and having an electro-conductive part installed below the upper package to be electrically connected to a lower terminal of the upper package;

a vacuum picker mounted on a center of the upper test socket to be able to vacuum-adsorb the lower package; and

an inelastic insulating sheet installed between the upper test socket and the upper package, the inelastic insulating sheet having a through hole formed at a position thereof corresponding to the terminal of the upper package and the electro-conductive part, and having a vacuum space part formed in a lower surface thereof corresponding to the upper test socket.