An antenna includes a split-ring conductive portion and a ring-inside conductive portion. The split-ring conductive portion is positioned outside a region and is positioned in an area which extends along an outline of the region except for a split. The ring-inside conductive portion is positioned inside the region. The ring-inside conductive portion is continuous with one of parts of the split-ring conductive portion, the split being put between the parts of the split-ring conductive portion. At least a part of the ring-inside conductive portion is bent so as to extend parallel to the split-ring conductive portion.