A wire antenna comprises a main radiating element, a grounding element, a shorting element, and a coaxial cable. The said main radiating element and the said grounding element are linked by the said shorting element. A central conducting wire and an outer grounding conductor of the coaxial cable are electrically connected to the first and the second points on the said main radiating element and the said grounding element respectively. The main radiating element and the grounding element are all made of a single metal wire with compact size and low cost. The present invention is capable of single or dual-band operation for applications in WLAN devices.