PURPOSE: To shorten the antenna element length by covering an antenna element with a hollow element cover made of a material of a high dielectric constant which has a larger external size than the element.

CONSTITUTION: A hollow columnar element cover 14 is externally fitted to a columnar antenna element 12. The external size d2 of the cover 14 is larger than the external size d1 of the element 12 by several to several tens times. The cover 14 uses a polycarbonate material having a high dielectric constant. The contraction factor is set at 71% when the sizes d1 and d2 are set at 2mm and 30mm respectively. While the length l2 of the element 12 is set at 5.7cm and can be shortened by increasing the size d2.