A broadside antenna includes a first radiation element and a second radiation element arranged at an interval, a first grounding element and a second grounding element arranged at an interval, and a first excitation element. A first gap is formed between the first radiation element and the second radiation element. The first excitation element includes a first feeding structure and a first extension stub that are arranged at an interval. The first feeding structure includes a first feed-in part connected to a feed source. The first extension stub is located on a side of the first feeding structure adjacent close to the first feed-in part. The first extension stub includes a first grounding part adjacent to the first feed-in part. The first grounding part is connected to the grounding surface.