PURPOSE: To shorter a processing step by determining a histogram accumulated value till the next time series data is inputted every time when one of time series data is inputted and calculating the accumulated values of plural maximum accumulated values with each other in each block.

CONSTITUTION: In an address arithmetic circuit 6, time series data is outputted as address data ADij and the contents of a word memory is increased by one. Next, address data ADij+1 is outputted, the contents of the word memory is increased and a histogram accumulated value is determined. At the point of time when the input of time series data is terminated by repeating a sequence every time when time series data is inputted, the histogram accumulated value for each block is determined. When the input is terminated, the address of the word memory is outputted in the address arithmetic circuit 6, a second multiplexer 3 is switched so as to transmit the output of a register 5 to an adder 2 and the maximum accumulated value of the highest order word memory of each block is calculated.