A burn-in socket includes a base, a sliding plate mounted to the base and having a number of pin holes, a number of contacts secured to the base and an actuator mounted on the base. The contacts each comprise a base portion and a pair of arms received in the pin holes of the sliding plate. The actuator includes a frame and a number of actuating portion for driving the sliding plate to move in a transversal direction. The sliding plate includes a number of projections adjacent to contacts. Each projection and the pair of arms of an adjacent contact together define a receiving space and located at three sides of the receiving space, respectively.