According to one embodiment, an antenna device includes a feeding portion, first and second wire-like metal portions, third and fourth plate-like metal portions and a fifth metal portion. One ends of the first and second wire-like metal portions are connected to the feeding portion. The third and fourth plate-like metal portions are respectively connected to the other ends of the first and second metal portions and disposed separately from each other with a predetermined distance therebetween. The fifth metal portion is configured to connect the third metal portion to the fourth metal portion. A total electrical length of the first to fifth metal portions is 3/2 wavelength at operating frequency band.