An antenna for wireless communications includes a horizontal polarization antenna and a vertical polarization antenna that are disposed in a stacked manner. The horizontal polarization antenna includes a radiation element and a double-sided parallel strip line. One end of the double-sided parallel strip line is connected to the radiation element. A length range of the double-sided parallel strip line is 0.58 to 1.35 times a waveguide wavelength of an electromagnetic wave in the double-sided parallel strip line at an operating frequency of the vertical polarization antenna.