1. A video signal identification device that determines whether a signal format of an input video signal is an RGB signal or a Y/color difference signal, the video signal identification device comprising: a clamp circuit that clamps the input video signal to adjust a pedestal level of the input video signal to a predetermined signal level and outputs the clamped video signal; an AD conversion circuit that receives the video signal output from the clamp circuit; a video signal-relating information acquisition module that acquires a preset piece of video signal-relating information, in response to an output video signal from the AD conversion circuit; and a video signal identification module that obtains an RGB probability, which represents a possibility that the signal format of the input video signal is the RGB signal, and a color difference probability, which represents a possibility that the signal format of the input video signal is the Y/color difference signal, based on the preset piece of video signal-relating information acquired by the video signal-relating information acquisition module, and compares the RGB probability with the color difference probability to determine whether the signal format of the input video signal is the RGB signal or the Y/color difference signal.