A request change unit outputs a command as a request under control of a judgment control unit. A response condition determination unit determines a condition that is to be matched by a correct response which is to be returned from the other device-in-communication in reply to the command if the other device-in-communication operates in conformity with a protocol. A check unit checks a response received from the other device-in-communication in reply to the command, against the condition. If the received response does not match the condition but is correctable to match the condition as a result of the check, a response correction unit corrects the received response to match the condition under control of the judgment control unit.