A control apparatus with a fast I/O function is adapted for storage of a control program, and to input a status of a target to be controlled as an input data from an I/O device, follow the control program to execute an operation of the input data, and output to the I/O device a result of the operation as an output data for controlling the target to be controlled, and includes a batch I/O buffer memory 201 having an output data register for storing an output data of the I/O device, and a batch I/O buffer memory controller 203 for controlling a writing of output data to be written to the batch I/O buffer memory 201, the batch I/O buffer memory controller 203 being adapted to control the writing of output data to the batch I/O buffer memory in accordance with a comparison output of control data of a control program executing circuit 14.