There is provided an antenna device of a radio apparatus, including a fed partial element, a folded partial element and an open-ended partial element. The fed partial element is formed to be extended from a fed portion to a first branch portion where the folded partial element branches off. The folded partial element has a grounded end and has a forward path and a backward path short-circuited to each other. The folded partial element and a path on the fed partial element from the fed portion to the first branch portion have a summed length of about a half wavelength of a first frequency. The open-ended partial element branches off at a second branch portion. The open-ended partial element and a path on the fed partial element from the fed portion to the second branch portion have a summed length of about a one-fourth wavelength of a second frequency.