An antenna (10, 10A) mountable on an object, wherein: the antenna comprises a main portion, a facing portion, a first feeding terminal, a second feeding terminal (50, 501, 503, 505) and an additional terminal; the main portion has a ring-shape with a split and has a first end portion and a second end portion which form the split; the facing portion has a first facing portion provided on the first end portion and a second facing portion provided on the second end portion; the first facing portion and the second facing portion are arranged apart from each other and face each other; the first feeding terminal is situated nearer to the first end portion on the main portion than the second feeding terminal is situated; and the additional terminal is situated nearer to the second end portion on the main portion than the second feeding terminal is situated, the first feeding terminal, the second feed terminal and the additional terminal are provided on the main portion and are parts which are fixable to the object when the antenna is mounted on the object; each of the first feeding terminal and the additional terminal has a first part (401, 601) extending in an inward direction directed inward of the main portion from the main portion and a second part (403, 603) extending from an end of the first part in an intersecting direction intersecting with the inward direction and perpendicular to a plane on which the main portion is provided; and the second part is fixable to the object when the antenna is mounted on the object, characterized in that the antenna is made of a single metal sheet having a first bent part, a second bent part and a third bent part; the second part of the first feeding terminal extends from the end of the first part of the first feeding terminal via the first bent part; the second part of the additional terminal extends from the end of the first part of the additional terminal via the second bent part; and the second feeding terminal extends from the main portion via the third bent part. the antenna comprises a main portion, a facing portion, a first feeding terminal, a second feeding terminal (50, 501, 503, 505) and an additional terminal; the main portion has a ring-shape with a split and has a first end portion and a second end portion which form the split; the facing portion has a first facing portion provided on the first end portion and a second facing portion provided on the second end portion; the first facing portion and the second facing portion are arranged apart from each other and face each other; the first feeding terminal is situated nearer to the first end portion on the main portion than the second feeding terminal is situated; and the additional terminal is situated nearer to the second end portion on the main portion than the second feeding terminal is situated, the first feeding terminal, the second feed terminal and the additional terminal are provided on the main portion and are parts which are fixable to the object when the antenna is mounted on the object; each of the first feeding terminal and the additional terminal has a first part (401, 601) extending in an inward direction directed inward of the main portion from the main portion and a second part (403, 603) extending from an end of the first part in an intersecting direction intersecting with the inward direction and perpendicular to a plane on which the main portion is provided; and the second part is fixable to the object when the antenna is mounted on the object, characterized in that the antenna is made of a single metal sheet having a first bent part, a second bent part and a third bent part; the second part of the first feeding terminal extends from the end of the first part of the first feeding terminal via the first bent part; the second part of the additional terminal extends from the end of the first part of the additional terminal via the second bent part; and the second feeding terminal extends from the main portion via the third bent part.