PURPOSE: To provide an arithmetic circuit in which time to be required for moving average arithmetic processing is shortened and a video signal processing processor capable of efficiently executing video signal processing by the use of the arithmetic circuit.

CONSTITUTION: A working buffer or an I/O buffer is accessed in each clock cycle and picture element data xk are inputted from an input terminal X to an adding circuit 304 and a register 400. The register 400 outputs picture element data xk-1 inputted in the preceding) clock cycle to a selector circuit 402 through a selector circuit 308. An accumulating circuit 304 mutually adds the picture element data xk, xk-1 and outputs the added result from an output terminal A.