PURPOSE: To promptly detect the no-response fault of terminal equipment by sampling a necessary time when control data are inputted/outputted between a CPU and the terminal equipment normally, and determining a monitoring time.

CONSTITUTION: An input/output control detecting part 11, an input/output necessary time counting part 12, and the monitoring time setting part 13 are provided. At the time of the input/output repeated between the CPU and the terminal equipment in a first mode, the maximum value of the input/output necessary time in a certain range is obtained as a monitoring time maximum value, in a second mode at the time of deciding the normality of the terminal equipment, the necessary time is fetched as sampling data, the monitoring time optimum value is determined with the use of the newest constant value, and it is used for the monitor of the terminal equipment fault. Only when the necessary time exceeds the monitoring time optimum value, the monitoring time maximum value obtained in the first mode is used for the monitoring time instead of the optimum value, and the terminal equipment is finally decided. Thus the terminal equipment can be efficiently decided.