A parallel operation histogramming device can handle parallel-input data from a plurality of processors to generate frequency data of a histogram. The processing time for generating frequency data of the histogram is independent of the distribution of histogram values in the input data. The device can also reduce the memory area used for accumulating frequency data of the histogram. The device includes a histogram counter circuit which has a plurality of counters equal in number to the number of histogram bins. The counters count in parallel the number of pieces of data for each type of the operation results from the plurality of processors. The counted values from each counter are accumulated to form the frequencies in a histogram.