A multiconductor plug (10) has exposed electrodes (11a through 11e) on a shaft portion (14) and an electrode (11f) located at an annular flat portion of a flange portion (15) perpendicular to an axial direction. A multiconductor jack (20) has a casing (21) forming a space capable of being occupied by the shaft portion (14) of the multiconductor plug (10), electrically conductive terminals (23a through 23e) that come into electrically conductive contact with the electrodes (11a through 11e) of the shaft portion (14) of the multiconductor plug (10), and an electrically conductive terminal (23f) having a contacting portion (23f1) for making electrically conductive contact with the flat electrode (11f) perpendicular to the axial direction and an elastic portion (23f3) that extends in the axial direction. The contacting portion (23f1) of the electrically conductive terminal (23f) presses against the electrode (11f) as a result of elastic forces parallel to the axial direction.