PURPOSE: To eliminate the need of a clock signal, and to shorten the sorting time by comparing a large/small relation of plural input data in a round robin, adding up the result of comparison and outputting is as priority of the corresponding input data.

CONSTITUTION: When input data inputted to an input terminal 20 is taken notice of, a comparator 401 compares it with input data of an input terminal 21, and in a buffer in which the latter is larger, an output signal becomes significant. In comparators 402-406, as well, in the same way, input data inputted to input terminals 22-27 are larger than that of the input terminal 20, and output signals become significant, respectively. Results of comparison of each comparator 401-407 are sent to an adder 60, respectively, and the number of significant output signals is counted. The input data inputted to the input terminals 21-27 are also the same, compared with the input data of the input terminals 20-27 by comparators 410-417...470-476, respectively, and the number of input data being larger than them is added up, and outputted as priority from output terminals 51-57.