An antenna structure includes an antenna pattern, a ground layer and two microstrip lines. The antenna pattern includes a first portion and a second portion. The first portion is rectangle shape and includes a first, a second, a third and a fourth sides. The second portion protrudes outwardly from the first side and the second side. The ground layer has two slots. Projections of the two slots to the antenna pattern are close to the third and the fourth sides. Projections of the two microstrip lines to the antenna pattern are perpendicular to the third and the fourth sides. Each microstrip line has a first section and a second section. Projection of the second section to the antenna pattern is closer to a center of the first portion than projection of the first section. A width of the first section is greater than a width of the second section.