A data transmitting device may include a first data transmitting unit and a second transmitting unit. The second data transmitting unit transmits to an external device video data encoded so as to be DC-free and capable of clock regeneration, via a pair of AC-coupled lines as a transmission path. Accordingly, it is possible to increase the transmission bandwidth of video data while improving signal quality and reducing power consumption. In addition, bi-directional transmission may be allowed which may enable new applications for inter-room transmission and the like.