PURPOSE: To execute the arithmetic processing with high accuracy by bringing a coefficient to 2n multiple, multiplying it as a coefficient in which a difference of the maximum value and the minimum value of its value becomes two folds or below by plural input signals, respectively, and also, bringing a result of each multiplication to 2-n multiple in accordance with 2n multiple of the coefficient and adding them.

CONSTITUTION: Input digital data A - D are converted into serial data by P-S converting circuits 38 - 41, respectively, and thereafter, supplied to multiplying circuits 42 - 45, and coefficient data of 8 bits stored in each coefficient ROM 46 - 49 are multiplied. In this case, the coefficient data stored in each coefficient ROM 46 - 49 are multiplied in advance by 2n(n = 0, ±1, ±2, ±3,...), and corrected so that a difference of the maximum value and the minimum value thereof becomes two folds or below. Subsequently, a result of this multiplication is supplied to S-P converting circuits 50 - 53, respectively, and converting into parallel data of 8 bits or more, based on a clock outputted from a timing control circuit 54. In such a way, an arithmetic processing of high accuracy can be executed without increasing the number of bits of data.