PURPOSE: To improve the accuracy of calculation of similarity of pattern, by obtaining a minimum interval for each characteristic vector and adding the values for all the characteristic vectors, through mutual shift of characteristic vector between two compared patterns within a predetermined range.

CONSTITUTION: A characteristic vector of a pattern P to be compared is set to the 1st pattern memory 1, and a characteristic vector of the other pattern P0 to be compared is set to the 2nd pattern memory 2. The vectors set to each are shifted at the 1st and 2nd shift registers 3 and 4 respectively and sequentially read out and further inputted to the 1st, 2nd and 3rd differential operation sections 5W7. The absolute value of the difference of the two characteristic vector is obtaind at the sections 5, 6 and 7 respectively and the absolute value is applied to a minimum value operating section 8. The minimum value of the result of operation is obtained at the section 8, the minimum value is stored in a register 9 via an addition circuit 10, and the interval of all the characteristic vectors is outputted from the circuit 10 under the control of a control section 11.