An antenna apparatus is disclosed including an antenna element; an installation base being a base where the antenna element is installed; a container including an upper surface that opens and housing the antenna element and the installation base, the upper surface being a surface closest to a ground surface when the container is installed in a ground; and a cover being formed of FRP (Fiber-Reinforced Plastics) and covering an opening of the container, wherein the installation base includes a height adjustment mechanism that adjusts a distance from the antenna element to the cover. In other aspects, a radio base station is also disclosed.