An antenna apparatus comprising: a first receiving antenna and a second receiving antenna respectively disposed at positions on a plane which are in an equal distance from a reference point and face each other with the reference point therebetween; a third receiving antenna and a fourth receiving antenna disposed at positions on the plane, a gravity center of the third receiving antenna and a gravity center of the fourth receiving antenna being in an equal distance from the reference point on the plane, a straight line connecting the gravity centers of the third receiving antenna and the fourth receiving antenna being at an angle of 90 degrees with respect to a straight line connecting a gravity center of the first receiving antenna and a gravity center of the second receiving antenna; and a fifth receiving antenna, a sixth receiving antenna, a seventh receiving antenna, and an eighth receiving antenna disposed respectively at positions on the plane, gravity centers of the fifth to eighth receiving antennas (45 to 48) being on straight lines different from each other, which are rotated by an angle of 45 degrees from the straight line connecting the gravity centers of the first receiving antenna and the second receiving antenna and the straight line connecting the gravity centers of the third receiving antenna and the gravity center of the fourth receiving antenna, respectively, wherein the first to eighth receiving antennas (41 to 48) are configured by dipole antennas, formed such that two conductive wires symmetrically extend to left and right sides to be in a straight line and have a same length; characterized in that each of the first to eighth receiving antennas (41 to 48) is disposed on a plate unit formed of a sheet-like flexible substrate; and the plate unit includes a positioning unit configured to position the antenna apparatus with respect to a target object to which the antenna apparatus is mounted. a first receiving antenna and a second receiving antenna respectively disposed at positions on a plane which are in an equal distance from a reference point and face each other with the reference point therebetween; a third receiving antenna and a fourth receiving antenna disposed at positions on the plane, a gravity center of the third receiving antenna and a gravity center of the fourth receiving antenna being in an equal distance from the reference point on the plane, a straight line connecting the gravity centers of the third receiving antenna and the fourth receiving antenna being at an angle of 90 degrees with respect to a straight line connecting a gravity center of the first receiving antenna and a gravity center of the second receiving antenna; and a fifth receiving antenna, a sixth receiving antenna, a seventh receiving antenna, and an eighth receiving antenna disposed respectively at positions on the plane, gravity centers of the fifth to eighth receiving antennas (45 to 48) being on straight lines different from each other, which are rotated by an angle of 45 degrees from the straight line connecting the gravity centers of the first receiving antenna and the second receiving antenna and the straight line connecting the gravity centers of the third receiving antenna and the gravity center of the fourth receiving antenna, respectively, wherein the first to eighth receiving antennas (41 to 48) are configured by dipole antennas, formed such that two conductive wires symmetrically extend to left and right sides to be in a straight line and have a same length; characterized in that each of the first to eighth receiving antennas (41 to 48) is disposed on a plate unit formed of a sheet-like flexible substrate; and the plate unit includes a positioning unit configured to position the antenna apparatus with respect to a target object to which the antenna apparatus is mounted.