a moving averaging filter which does not propagate a calculation error is provided reducing the size of the hardware . this moving average filter has a data holding unit for holding multiple successive data , a coefficient storing unit for storing coefficients , a first adder which calculates the sum of a pair of data of a prescribed combination held in the data holding unit , a multiplier which multiplies the sum to coefficient data obtained from the coefficient storing unit , and a second adder which adds up - a prescribed number of multiplication results produced by the multiplier .