In a processing system including a processing apparatus, an input/output apparatus and communication apparatuses, the communication apparatus includes: a first instructing unit that issues a configuration change instruction in accordance with set configuration information to the processing apparatus and the input/output apparatus; and a first setting unit that, when an operation change completion notification corresponding to the configuration change instruction is received, sets the configuration information in accordance with a state established after a configuration change, and each of the processing apparatus and the input/output apparatus includes: a second setting unit that sets the configuration information in accordance with the configuration change instruction received from the communication apparatus; a second instructing unit that issues an operation change instruction in accordance with the set configuration information; and a notifying unit that, when the operation change is completed, issues an operation change completion notification to the communication apparatus.