The invention relates to an antenna device, which comprises a basic plate, an antenna unit, several conductive through holes and a narrow slit. Wherein, the basic plate is made from insulated material, whose upper and lower surfaces individually have a earthing area and a insulated area; the earthing area of lower surface has the first metallic layer; the earthing area of upper surface has the second metallic layer; the antenna unit is made on the insulated area of upper surface, which comprises a antenna main body and a feedback electric pin; said conductive through holes are arranged insidethe basic plate to electrically connect the first and second metallic layers and guide the coupling current generated by the second metallic layer into the first metallic layer; and the narrow slit ison the first metallic layer with a preset length to increase the equivalent current length of the coupling current that input into the first metallic layer, to improve the gain of antenna device.