PURPOSE: To precisely input a signal which varies fast to an input/output control circuit with a small hardware quantity by varying the relative rate of the frequency of sampling of respective input data according to a processor's indication.

CONSTITUTION: A user describes a control program 24 of the sequence controller 100 on a computer 25. The described control program 24 is properly compiled by the computer 25 and then transferred to the memory in the processor 2 of the sequence controller 100. Then the processor 2 of the sequence controller 100 executes the transferred control program 24 and controls a controlled system 200. Here, the processor 2 controls the frequency of the sampling of data by the input/output control circuit 1 from input circuits 4, 5, and 6 according to the control program 24. Therefore, the user can optionally set the relative rate of the sampling frequency of the sampling of the input data.