An electrical connector is provided with a plug portion having an upper surface on which electronic components can be disposed, and a receptacle portion for mounting on a circuit board. In the plug portion, a central recess is formed, which extends downwardly within the body of the receptacle portion so that the electronic components are disposed at least partially within the central recess. The plug portion has, on its lower surface side, plug side contacts that serve as electrical contacts with a terminal of the receptacle portion, and has a protruding portion for engaging the connector receptacle portion. The plug side contacts and the protruding portion are positioned outside of the central recess higher than a bottom plate portion which forms a bottom of the central recess.