According to one embodiment, a transmission apparatus includes a transmission module, a controller, a signal transmission module, and a selection module. The transmission module is configured to output a video signal or an audio signal to a TMDS line of an HDMI cable in a form based on the HDMI standard. The controller is configured to input/output an HEAC signal of the HDMI standard. The signal transmission module is configured to perform signal transmission based on a method other than the HDMI standard. The selection module is configured to selectively switch the HEAC line of the HDMI cable to either a state used for transmission of the HEAC signal that is input/output to/from the controller or a state used for transmission of a signal that is input/output to/from the signal transmission module.