A beam forming antenna in which directivity directions of beams can be controlled at higher resolution of control is provided. The beam forming antenna includes a matrix circuit having multiple final output terminals and multiple antenna elements connected to the multiple final output terminals respectively. The matrix circuit includes a first sub-matrix, a second sub-matric, and adders which combine outputs of the first sub-matrix and outputs of the second sub-matrix. By selecting any input terminal out of the multiple input terminals of the first sub-matrix or the multiple input terminals of the second sub-matrix and inputting a signal, a signal having a predetermined phase difference between output terminals is output at the multiple final output terminals and the phase difference between output terminals has a differing value according to a selected input terminal.