1. A vector waveform rotation device ( 60 ) for rotating a vector waveform displayed on a vector scope, comprising means ( 6 ′) for inputting a first color difference signal (B-Y signal) and a second color difference signal (R-Y signal) demodulated from a chrominance signal of a composite video signal as x and y, and rotating a vector (x, y)&equals;(first color difference signal, second color difference signal).