1. A sampled-data I-PD control apparatus for an interference N-(positive integer not less than 2), input/N-output process comprising: control error calculating means for calculating respective differences between N outputs of the process and corresponding N set-point values to generate N control errors; sampled-data I-PD controller means for calculating the N outputs of the process and the N control errors in accordance with sampled-data I-PD control parameters to obtain N control variables, and for supplying the N control variables to N inputs of the process; identification signal generating means for respectively supplying N persistently exciting identification signals to the N inputs of the process; identifying means for identifying a pulse transfer function of the process in accordance with the N inputs and the N outputs of the process while the N persistently exciting identification signals are supplied to the N inputs; S-transfer function calculating means for transforming an identified transfer function to an S-transfer function; and tuning means for calculating an S-transfer function from the set-point values to the process outputs in accordance with a transformed S-transfer function, matching the calculated S-transfer function with an S-transfer function from the set-point values to the process outputs of a noninterference N-input/N-output process model, and tuning the sampled-data I-PD control parameters in accordance with a matching result.