Electrical connector and transmission line

An electrical connector (1) includes a first connector (2) having first contacts (24a-24d); and a second connector (3) having second contacts (34a-34d) which are brought into contact with the first contacts when the second connector is fitted to the first connector, wherein an outer conductor (25), which is formed to nearly entirely surround all the first contacts (24a-24d) and the second contacts (34a-34d) when the first connector and the second connector are fitted to each other, is held in at least either of the first connector and the second connector; and wherein one or more shielding conductors (26,35), which cooperate with the outer conductor (25) to nearly entirely surround each of the first and second contacts and are held equal in potential to the outer conductor, when the first connector (2) and the second connector (3) are fitted to each other, are held in at least either of the first connector and the second connector.