Conventional coaxial wiring devices present a problem in that the management of the manufacturing process therefor is difficult. A coaxial wiring device according to the present invention includes a first member, a second member, and a conductor plate. The first member (10) and the second member (30) include, when a line that connects a first port and a second port is denoted by a reference line, a first groove (11) that has a central point on the reference line and extends in a direction that intersects with the reference line; a second groove (12) that connects one end (FN1) of the first groove (11) and the first port; a third groove (13) that connects the other end (FN2) of the first groove (11) and the first port and has a shape that is line symmetrical to the second groove (12) with respect to the reference line; a fourth groove (14) that connects one end (FN1) of the first groove (11) and the second port; and a fifth groove (15) that connects the other end (FN2) of the first groove (11) and the second port and has a shape that is line symmetrical to the fourth groove (14) with respect to the reference line.