An antenna device comprising: a shielded cable having a first connection portion on one end side and a second connection portion on the other end side; and an antenna element which is connected to a first outer conductor of the shielded cable at the second connection portion of the shielded cable, wherein the shielded cable includes an inner conductor , a first insulator , the first outer conductor , a second insulator , and a second outer conductor , which are coaxially disposed in this order from an inner side, and is covered at its outer circumference by an insulation sheath , the first connection portion of the shielded cable is formed such that the inner conductor is configured to be supplied with power and the first outer conductor is connectable to a ground, and in the second connection portion of the shielded cable, the inner conductor is connected to the second outer conductor ; wherein the first outer conductor is formed by a braided shield which is braided by a plurality of element wires having an electrically-conductive property; characterised in that : a coupling state of the second insulator and the first outer conductor is coarser than a coupling state of the second insulator and the second outer conductor ; the second insulator is formed of polyethylene and is formed by an extrusion molding process carried out at a temperature greater than the melting point of the polyethylene; and a seal film is disposed between the second insulator and the first outer conductor to prevent melted polyethylene resin to soak into the interwoven portion of the braided shield. a shielded cable having a first connection portion on one end side and a second connection portion on the other end side; and an antenna element which is connected to a first outer conductor of the shielded cable at the second connection portion of the shielded cable, wherein the shielded cable includes an inner conductor , a first insulator , the first outer conductor , a second insulator , and a second outer conductor , which are coaxially disposed in this order from an inner side, and is covered at its outer circumference by an insulation sheath , the first connection portion of the shielded cable is formed such that the inner conductor is configured to be supplied with power and the first outer conductor is connectable to a ground, and in the second connection portion of the shielded cable, the inner conductor is connected to the second outer conductor ; wherein the first outer conductor is formed by a braided shield which is braided by a plurality of element wires having an electrically-conductive property; characterised in that : a coupling state of the second insulator and the first outer conductor is coarser than a coupling state of the second insulator and the second outer conductor ; the second insulator is formed of polyethylene and is formed by an extrusion molding process carried out at a temperature greater than the melting point of the polyethylene; and a seal film is disposed between the second insulator and the first outer conductor to prevent melted polyethylene resin to soak into the interwoven portion of the braided shield. a coupling state of the second insulator and the first outer conductor is coarser than a coupling state of the second insulator and the second outer conductor ; the second insulator is formed of polyethylene and is formed by an extrusion molding process carried out at a temperature greater than the melting point of the polyethylene; and a seal film is disposed between the second insulator and the first outer conductor to prevent melted polyethylene resin to soak into the interwoven portion of the braided shield. <EOS>