A rubber plug has a tubular sealing function portion that allows an electric wire to pass through the tubular sealing function portion and a tubular low-rigidity portion that allows the electric wire to pass through the low-rigidity portion. The sealing function portion exhibits sealing performance by elastically coming into close contact with the inner peripheral surface of the terminal accommodating chamber and the outer peripheral surface of the electric wire. The low-rigidity portion has a lower rigidity than the sealing function portion, and is arranged rearward of the sealing function portion.