PURPOSE: To offer the chrominance signal processor with the same time axis fluctuation-elimination characteristics by performing input while switching a conversion signal to be inputted to a second frequency converter at the time of switching the conversion frequency of a low frequency conversion chrominance signal in normal time and in band expansion time.

CONSTITUTION: In a second frequency converter 14, signals obtained by switching a reference carrier wave signal from a first reference oscillator 6 and a reference conversion signal from a second reference oscillator 19 by means of a switch 20 is also entered. The conversion output from the second frequency converter 14 is entered into a first band pass filter(BPF) 15 and a second band pass filter(BPF) 16, switched by a switch 17 to be outputted to a first frequency converter 2. Since the frequency conversion of a low frequency conversion carrier wave is performed by the conversion signal with the frequency adding a carrier wave signal and the prescribed conversion carrier wave signal, the switching in the normal time and band expansion time can be performed without changing transmission function.