Planar folded dipole antenna (PFDA) with feed line which is approximately quarter wavelength has been reported [1]. However, the feed line is too long to be mounted on a small terminal. In this paper, in order to amount the antenna to a small terminal for WiMAX, we investigate miniaturization of the feed line and characteristics of the antenna on the small ground plane (50 mm×80 mm). The planar folded dipole antenna on the ground plane has two resonance mode. Moreover, the impedance characteristic can be modified by adjusting the width of antenna and feed line. A proposed antenna has wideband characteristic which covers the bandwidth of 2.5 GHz band and 3.5 GHz band (2.3 GHz ∼ 3.8 GHz) for WiMAX with a feed line of approximately one eleventh wavelength.