A parallel calculation system includes a plurality of functional nodes and a plurality of network switches, which serve as part of a communication path for communication between the functional nodes and function as communication channels. As for the functional nodes, a functional node group made up of part or all of a plurality of the functional nodes that the parallel calculation system includes is managed as one group. The network switches include a plurality of input/output ports, which are ports for inputting and outputting the communication request, and a switch, which outputs the communication request that the input/output port inputs to the input/output port. The network switches manage a communication bandwidth for each of the communication channels between the functional nodes and control the switch.