A modular probe card comprises a printed circuit board, an interposer, and a probe head where the printed circuit board has a plurality of first contact pads, the probe head has a plurality of second contact pads. The interposer is disposed between the printed circuit board and the probe head where the interposer includes a substrate and a plurality of pogo pins. The substrate has a first surface, a second surface, and a plurality of through holes penetrating from the first surface to the second surface. The pogo pins are secured in the through holes of the substrate. Each of the pogo pins has a first contact point, a second contact point, and a spring therebetween, whereby the first contact points are elastically extruded from the first surface to contact the first contact pad, and the second contact points are elastically extruded from the second surface to contact the second contact pad, so as to overcome the poor electrical connections between the printed circuit board and the probe head through the interposer due to poor coplanarity of the first contact pads of the printed circuit board.