An antenna apparatus (107A, 107B) comprising at least one antenna (1A, 2A, 3A; 1B, 2B, 3B) and a ground conductor plate, wherein each of the at least one antenna (1A, 2A, 3A; 1B, 2B, 3B) comprises: a dielectric substrate (10, 20, 30) having a first surface and a second surface; a first feed element (11, 21, 31) having a strip shape and formed on the first surface of the dielectric substrate (10, 20,30), the first feed element (11, 21, 31) having a first end connected to a feeding point (13, 23, 33), and the first feed element (11, 21, 31) having an opened second end (11d, 21d, 31d); and a first parasitic element (12, 22, 32) having a strip shape and formed on the second surface of the dielectric substrate (10, 20,30), the first parasitic element (12, 22, 32) having a first end connected to the ground conductor plate, and the first parasitic element (12, 22, 32) having an opened second end (12d, 22d, 32d), wherein the first feed element (11, 21, 31) and the first parasitic element (12, 22, 32) are arranged to oppose each other, at least a portion including the second end of the first feed element (11, 21, 31) and the second end of the_first parasitic element, the antenna apparatus (107A, 107B) being characterized in that: each of the at least one antenna (1A, 2A, 3A; 1B, 2B, 3B) further comprises: a second feed element (15, 25, 35) having a strip shape and formed on the first surface of the dielectric substrate (10, 20, 30), the second feed element (15, 25, 35) having a first end and a second end, the first and second ends of the second feed element (15, 25, 35) being connected to different positions on the first feed element (11, 21, 31), respectively; and a second parasitic element (16, 26, 36) having a strip shape and formed on the second surface of the dielectric substrate (10, 20,30), the second parasitic element (16, 26, 36) having a first end and a second end, the first and second ends of the second parasitic element (16, 26, 36) being connected to different positions (12f, 12e) on the first parasitic element (12, 22, 32), respectively. a dielectric substrate (10, 20, 30) having a first surface and a second surface; a first feed element (11, 21, 31) having a strip shape and formed on the first surface of the dielectric substrate (10, 20,30), the first feed element (11, 21, 31) having a first end connected to a feeding point (13, 23, 33), and the first feed element (11, 21, 31) having an opened second end (11d, 21d, 31d); and a first parasitic element (12, 22, 32) having a strip shape and formed on the second surface of the dielectric substrate (10, 20,30), the first parasitic element (12, 22, 32) having a first end connected to the ground conductor plate, and the first parasitic element (12, 22, 32) having an opened second end (12d, 22d, 32d), wherein the first feed element (11, 21, 31) and the first parasitic element (12, 22, 32) are arranged to oppose each other, at least a portion including the second end of the first feed element (11, 21, 31) and the second end of the_first parasitic element, the antenna apparatus (107A, 107B) being characterized in that: each of the at least one antenna (1A, 2A, 3A; 1B, 2B, 3B) further comprises: a second feed element (15, 25, 35) having a strip shape and formed on the first surface of the dielectric substrate (10, 20, 30), the second feed element (15, 25, 35) having a first end and a second end, the first and second ends of the second feed element (15, 25, 35) being connected to different positions on the first feed element (11, 21, 31), respectively; and a second parasitic element (16, 26, 36) having a strip shape and formed on the second surface of the dielectric substrate (10, 20,30), the second parasitic element (16, 26, 36) having a first end and a second end, the first and second ends of the second parasitic element (16, 26, 36) being connected to different positions (12f, 12e) on the first parasitic element (12, 22, 32), respectively. each of the at least one antenna (1A, 2A, 3A; 1B, 2B, 3B) further comprises: a second feed element (15, 25, 35) having a strip shape and formed on the first surface of the dielectric substrate (10, 20, 30), the second feed element (15, 25, 35) having a first end and a second end, the first and second ends of the second feed element (15, 25, 35) being connected to different positions on the first feed element (11, 21, 31), respectively; and a second parasitic element (16, 26, 36) having a strip shape and formed on the second surface of the dielectric substrate (10, 20,30), the second parasitic element (16, 26, 36) having a first end and a second end, the first and second ends of the second parasitic element (16, 26, 36) being connected to different positions (12f, 12e) on the first parasitic element (12, 22, 32), respectively. a second feed element (15, 25, 35) having a strip shape and formed on the first surface of the dielectric substrate (10, 20, 30), the second feed element (15, 25, 35) having a first end and a second end, the first and second ends of the second feed element (15, 25, 35) being connected to different positions on the first feed element (11, 21, 31), respectively; and a second parasitic element (16, 26, 36) having a strip shape and formed on the second surface of the dielectric substrate (10, 20,30), the second parasitic element (16, 26, 36) having a first end and a second end, the first and second ends of the second parasitic element (16, 26, 36) being connected to different positions (12f, 12e) on the first parasitic element (12, 22, 32), respectively.