An HDMI apparatus and a method for controlling the same are provided. The HDMI apparatus includes an HDMI connection port, a control circuit, a master circuit, a slave circuit, and a switch circuit. The master circuit and the slave circuit are respectively configured to generate a master HDMI output signal and a slave HDMI output signal. The switch circuit is selectively conducted in a first conductive state and a second conductive state according to a control signal generated by the control circuit. In the first conductive state, the switch circuit is electrically connected to the master circuit, so that the master HDMI output signal is output through the HDMI connection port. In the second conductive state, the switch circuit is electrically connected to the slave circuit, so that the slave HDMI output signal is output through the HDMI connection port.