To provide a plane antenna which is applicable to short wavelengths and in excellent in dimensional precision, low in cost and good in productivity, and to provide its manufacturing method.

In the method for manufacturing the plane antenna, the plane antenna configured by coating a dielectric with a conductor has a pattern which is not coated with the conductor in a part of the surface of the dielectric coated with the conductor, and the manufacture has a step for integrally molding the dielectric and the pattern by injection molding while using a metal die having the pattern.