Abstract: A plurality of contact pins are embedded in a socket body having at least two mutually opposing parallel surfaces so as to correspond to the arrangement of a plurality of ball bumps of a BGA package. The tips of the plurality of contact pins protrude from one of the two parallel surfaces. A flat guide plate having a plurality of holes matched the arrangement and shape of the plurality of ball bumps, is elastically supported so as to be in a floating state with respect to the surface penetrated by the plurality of contact pins. And the flat guide plate houses a tip of one of the plurality of contact pins in each of the holes. The rim of the opening of each hole is in a tapered form so as to guide the center of a ball bump to within the limits of the outer form of the tip of a contact pin.