PURPOSE: To realize the video signal processing circuit of the picture-in-picture system to obtain an easy to see pattern by eliminating noise generated in the absence of a sub pattern video signal through the insertion of a specific background color signal.

CONSTITUTION: The processing circuit is provided with a background color generating circuit 7 generating a background color signal 21 representing a specific background color, a synchronizing signal detection circuit 3 detecting a synchronizing signal from a sub pattern video signal 12 to output a switching control signal 16, and a sub pattern signal changeover circuit 8 receiving a sub pattern signal 20 and the background color signal 21 and inputting the background color signal 21 to the main sub signal changeover circuit 9 in place of the sub pattern signal 20 when the sub pattern video signal 12 is not inputted according to the switching control signal 16.