A multi-antenna apparatus (10, 20, 30) comprising: a first antenna element (11, 21) and a second antenna element (12, 22); an ungrounded passive antenna element (13, 23), wherein said ungrounded passive antenna element (13, 23) includes a first opposing portion (131, 231) being arranged closer to said first antenna element (11, 21) than to the second antenna element (12, 22), and being opposed to said first antenna element (11, 21) a second opposing portion (132, 232) being arranged closer to said second antenna element (12, 22) than to the first antenna element (11, 21), and being opposed to said second antenna element (12, 22) and a coupling portion (133, 233) coupling said first opposing portion (131, 231) and said second opposing portion (132, 232) with each other, wherein the ungrounded passive antenna element (13, 23) is arranged between said first antenna element (11, 21) and said second antenna element (12, 22), and said first opposing portion (131, 231) and said second opposing portion (132, 232) are arranged within a region between the first antenna element (11,21) and the second antenna element (12, 22) characterized in that the ungrounded passive element is formed in a U-shape or an H-shape by the first opposing portion (131, 231), the second opposing portion (132, 232) and the coupling portion (133, 233). a first antenna element (11, 21) and a second antenna element (12, 22); an ungrounded passive antenna element (13, 23), wherein said ungrounded passive antenna element (13, 23) includes a first opposing portion (131, 231) being arranged closer to said first antenna element (11, 21) than to the second antenna element (12, 22), and being opposed to said first antenna element (11, 21) a second opposing portion (132, 232) being arranged closer to said second antenna element (12, 22) than to the first antenna element (11, 21), and being opposed to said second antenna element (12, 22) and a coupling portion (133, 233) coupling said first opposing portion (131, 231) and said second opposing portion (132, 232) with each other, wherein the ungrounded passive antenna element (13, 23) is arranged between said first antenna element (11, 21) and said second antenna element (12, 22), and said first opposing portion (131, 231) and said second opposing portion (132, 232) are arranged within a region between the first antenna element (11,21) and the second antenna element (12, 22) a first opposing portion (131, 231) being arranged closer to said first antenna element (11, 21) than to the second antenna element (12, 22), and being opposed to said first antenna element (11, 21) a second opposing portion (132, 232) being arranged closer to said second antenna element (12, 22) than to the first antenna element (11, 21), and being opposed to said second antenna element (12, 22) and a coupling portion (133, 233) coupling said first opposing portion (131, 231) and said second opposing portion (132, 232) with each other, wherein the ungrounded passive antenna element (13, 23) is arranged between said first antenna element (11, 21) and said second antenna element (12, 22), and said first opposing portion (131, 231) and said second opposing portion (132, 232) are arranged within a region between the first antenna element (11,21) and the second antenna element (12, 22)