Abstract: A color signal processing apparatus, particularly a circuit for generating a color sub-carrier wave for demodulation, used in a color television receiver set to demodulate a carrier color signal to reproduce a color image, is disclosed. The apparatus comprises an oscillation circuit including four differential amplifiers to synthesize oscillation signals having phases which differ 90.degree. from each other to produce a color subcarrier wave, a color-phase adjusting circuit for changing phases of the oscillation signals from the oscillation circuit by changing bias voltages of the differential amplifiers, and a phase detection circuit for comparing the phases of the oscillation signals having the phases changed by the color phase adjusting circuit with a phase of a color burst signal to change the bias voltages of the differential amplifiers in the oscillation circuit depending on the comparison.