A MIMO antenna apparatus includes a plurality of feeding antenna elements, a parasitic element electromagnetically coupled to each feeding antenna element, and a variable impedance load element connected to the parasitic element. A signal level comparator circuit detects received signal levels of received wireless signals and compares the received signal levels with each other, and thus detects the minimum received signal level. A controller controls an impedance value of the variable impedance load element based on the received signal levels detected by the signal level comparator circuit, such that the received signal level of the wireless signal having the minimum received signal level is substantially maximized.