A helical antenna includes a hollow cylindrical member having an inner peripheral surface and an outer peripheral surface, an antenna pattern film wound around the outer peripheral surface of the hollow cylindrical member, a center rod coaxial with a center axis of the hollow cylindrical member, and at least three ribs disposed between the center rod and the inner peripheral surface of the hollow cylindrical member. The ribs symmetrically extend in a radial manner at equal angular intervals. The hollow cylindrical member, the center rod, and the ribs preferably may be integrally molded out of plastic. The antenna pattern film may include a flexible insulator film and a conductive pattern formed on the flexible insulator film. The conductive pattern has at least one antenna lead member which is wound around the outer peripheral surface of the hollow cylindrical member in a helix fashion.