A blue stretch circuit of this invention has a first voltage detection circuit and a second voltage detection circuit, each of which detects that an amount of each of the first and the second color difference signals are within a predetermined range, a blue stretch control circuit which generates a control signal for blue stretching according to output signals of the voltage detection circuits and a level of a brightness signal and a B drive circuit to amplify a blue color signal according to an output signal of the blue stretch control circuit.