In the sequence program (ladder circuit), in order to give a common address between contacts of the ladder circuit longitudinally and store states before and after the processing of the contact in the ladder circuit, two types of memories corresponding to addresses at the both ends of the contact are provided and a compiler for classifying the processing into the five types and a sequence execution unit for processing a machine language of the compiler are further provided so that execution can be made even if an output instruction is provided in an intermediate portion of the ladder circuit.