An antenna apparatus is provided, which removes dead directions, and at the same time, has a suppression means for easily suppressing the change of an antenna directivity pattern caused by the effect of a feed line or a radome and an improvement means for simply improving the VSWR deterioration caused by the effect of a reflector or the radome. The antenna apparatus includes a sleeve antenna connected to a coaxial cable and a reflector in the shape of a cone, the sleeve antenna including a central conductor and a sleeve, in which the sleeve antenna is arranged in a concave portion of the cone so that the central conductor is aligned with a central axis of the cone, and a top end of the central conductor is separate from a vertex portion of the cone.