A burn-in socket comprises a base, a plurality of terminals received in the base, a lid mounted upon the base, and a sliding member mounted on the base. The terminal has a movable arm and a static arm, the lid has a number of actuating portions downwardly extending from the bottom thereof to drive the sliding member. The actuating portion of the lid drives the sliding member to move in both a longitudinal direction and a transverse direction, so that the movable arm moves not only in the longitudinal direction but also in the transverse direction to avoid interference with a static arm of an adjacent terminal.