A USB socket is a receptacle for a directional USB plug including a male tongue provided with a first electrode terminal, and has first and second female tongues and a casing. The first female tongue has a second electrode terminal electrically connected to the first electrode terminal when the USB plug is inserted in a regular orientation, and is pushed with the male tongue in a direction of insertion when the USB plug is inserted in an inverted orientation. The second female tongue is pushed with the male tongue in the direction of insertion when the USB plug is inserted in the regular orientation, and has a third electrode terminal electrically connected to the first electrode terminal when the USB plug is inserted in the inverted orientation. The casing houses the first and second female tongues such that the second and third terminals are face with each other.