The invention relates to a base station antenna, which comprises an antenna module with a plurality of vibrators arranged in the form of an array and a metamaterial module arranged corresponding to the vibrators; the metamaterial module comprises at least one metamaterial sheet layer; a region on each metamaterial sheet layer just aligned with each vibrator forms a refractive index distribution region; a plurality of mutually parallel refractive index straight lines are formed in each refractive index distribution region; a refractive index straight line in each refractive index distribution region is used as a dividing line; a plurality of adjacent refractive index straight lines at each side of the dividing line belong to one set, so that a plurality of square regions are formed; refractive indexes of various points on the same refractive index straight line in each square region are same; along with increasing of the distance from the refractive index straight line to the dividing line, the refractive index of each refractive index straight line is reduced; the reduction amount is increased; and both the refractive index of the refractive index straight line closest to the dividing line and the refractive index of the refractive index straight line farthest from the dividing line in each square region are equal respectively; therefore, the directivity and the gain of the antenna are increased.