A USB receptacle mateable with a USB plug along a mating direction is disclosed. The USB receptacle comprises a holder member made of insulator, a shell made of conductor, and a detection pin made of conductor which is separated and is different from the shell. The detection pin is made of resiliently-deformable material and is held by the holder member so as not to be in direct contact with the shell. The detection pin includes a first contact portion and a second contact portion. The first contact portion and the second contact portion pinch a part of a plug shell of the USB plug when the USB receptacle is mated with the USB plug. Under a condition where the USB receptacle is not mated with the USB plug, the first contact portion and the second contact portion meet an inequality of “(b−a)