An electrical connector includes an insulating housing and a plurality of first terminals. A front surface of the insulating housing is recessed rearward to form an insertion space. The insulating housing opens a plurality of first terminal grooves. The insulating housing defines a plurality of upper adjusting slots. The plurality of first terminals are disposed in the plurality of the first terminal grooves. Each of the plurality of the first terminals has a first fastening portion and a first contact portion. A rear end of the first fastening portion extends downward to form an adjusting portion which opens an opening. The first fastening portions of the plurality of the first terminals are assembled in the plurality of the upper adjusting slots. The first contact portions of the plurality of the first terminals are assembled in the plurality of the first terminal grooves and project downward into the insertion space.