The small loop antenna element of the antenna apparatus includes loop antenna portions that have a predetermined loop plane and radiate a first polarized wave component parallel to the loop plane, and at least one connecting conductor that is provided in a direction orthogonal to the loop plane and connects the plurality of loop plane portions to radiate a second polarized wave component orthogonal to the first polarized wave component. In the case of the antenna apparatus located adjacent to a conductor plate, by making the maximum value of the antenna gain of the first polarized wave component and the maximum value of the antenna gain of the second polarized wave component substantially identical when the distance between the antenna apparatus and the conductor plate is changed, a composite component of the first and second polarized wave components are made substantially constant regardless of the distance.