A parallel processing unit includes a plurality of main processing units and a decision processing unit. Each of the plurality of main processing units includes a main processing calculator for performing a calculation on one or more inputs, a main processing adder for adding an output of the main processing calculator and an output of a decision processing delayer, and a main processing comparator for making a comparison with an output of the main processing adder. The decision processing unit includes a decision processing calculator for adding outputs of the plurality of main processing calculators, a decision processing adder for adding an output of the decision processing calculator and the output of the decision processing delayer, the decision processing delayer for delaying an output of the decision processing adder, and a decision processing comparator for making a comparison with the output of the decision processing adder.