Antenna, antenna-attached device, and antenna-attached window glass for vehicle

An antenna comprising:

• a feeding portion comprising a first feeding portion and a second feeding portion and defining a gap therebetween;
• and
• a loop element including a first end and a second end, the first end being connected to the first feeding portion, and the second end being connected to the second feeding portion,
• wherein the loop element has a first element portion and a second element portion, which appear to face each other in a vertical direction in an elevation view as seen in a direction parallel with a horizontal plane,
• wherein a first gap is provided in a middle of the first element portion, and a second gap is provided in a middle of the second element portion,
• wherein the loop element has a first antenna conductor connected to the feeding portion and a second antenna conductor not connected to the feeding portion,
• wherein the first gap and the second gap are present between the first antenna conductor and the second antenna conductor,
• wherein a resonance of the loop element is reconfigurable between a first resonance mode and a second resonance mode, and
• wherein the first resonance mode is a reverse phase mode in which current flowing through the first antenna conductor is in an opposite direction to current flowing through the second antenna conductor.