An antenna apparatus comprising: a plurality of primary radiators for radiating radio waves; and a main reflector (2; 5; 7) for reflecting the radio waves radiated from the plurality of primary radiators, wherein the plurality of primary radiators is subdivided into a plurality of classes by combination of frequency and polarization of the radiated radio waves, each class comprises at least three primary radiators radiating radio waves having the same combination of frequency and polarization, and a plurality of primary radiators belonging to a same class is arranged, in a repeated triangle pattern in which a triangle is arranged repeatedly, at positions corresponding to vertexes of each triangle, wherein the repeated triangle pattern includes one or more triangles so as to form a same shape as the shape of the main reflector, and wherein an aperture shape of the main reflector is a non-rectangular parallelogram, wherein for each of the plurality of primary radiators sidelobes of a reflected beam are formed in two directions different from each other when projected on the plane of the repeated triangle pattern, and wherein for each of the plurality of primary radiators two line segments are defined as lines passing through the respective primary radiator and following the projection of the respective two directions on the plane of the repeated triangle pattern such that the first line segment passes through one or both of a top and bottom sides of the parallelogram of the repeated triangle pattern at a right angle and the second line segment passes through one or both of a left and right sides of the non rectangular parallelogram of the repeated triangle pattern at a right angle, or wherein the aperture shape of the main reflector is an equilateral triangle, wherein for each of the plurality of primary radiators sidelobes of a reflected beam are formed in three directions different from each other when projected on the plane of the repeated triangle pattern, and wherein for each of the plurality of primary radiators three line segments are defined as lines passing through the respective primary radiator and following the projection of the respective three directions on the plane of the repeated triangle pattern such that each line segment passes through a single side of the equilateral triangle of the repeated triangle pattern at a right angle. a plurality of primary radiators for radiating radio waves; and a main reflector (2; 5; 7) for reflecting the radio waves radiated from the plurality of primary radiators, wherein the plurality of primary radiators is subdivided into a plurality of classes by combination of frequency and polarization of the radiated radio waves, each class comprises at least three primary radiators radiating radio waves having the same combination of frequency and polarization, and a plurality of primary radiators belonging to a same class is arranged, in a repeated triangle pattern in which a triangle is arranged repeatedly, at positions corresponding to vertexes of each triangle, wherein the repeated triangle pattern includes one or more triangles so as to form a same shape as the shape of the main reflector, and wherein an aperture shape of the main reflector is a non-rectangular parallelogram, wherein for each of the plurality of primary radiators sidelobes of a reflected beam are formed in two directions different from each other when projected on the plane of the repeated triangle pattern, and wherein for each of the plurality of primary radiators two line segments are defined as lines passing through the respective primary radiator and following the projection of the respective two directions on the plane of the repeated triangle pattern such that the first line segment passes through one or both of a top and bottom sides of the parallelogram of the repeated triangle pattern at a right angle and the second line segment passes through one or both of a left and right sides of the non rectangular parallelogram of the repeated triangle pattern at a right angle, or wherein the aperture shape of the main reflector is an equilateral triangle, wherein for each of the plurality of primary radiators sidelobes of a reflected beam are formed in three directions different from each other when projected on the plane of the repeated triangle pattern, and wherein for each of the plurality of primary radiators three line segments are defined as lines passing through the respective primary radiator and following the projection of the respective three directions on the plane of the repeated triangle pattern such that each line segment passes through a single side of the equilateral triangle of the repeated triangle pattern at a right angle.