A sequence controller having a memory for storing predetermined control sequences, an operation device for sequentially reading the contents of the memory and executing the control sequences stored therein in accordance with externally supplied instructions, a programming panel for reading and displaying data from the memory and for writing the control sequence in the memory, bus lines coupled to the operation device and the panel, respectively, to permit parallel operation thereof without lowering the processing speed and to permit programming of the operation device without using conventional input-output instructions by supplying input and output data for operating an external controlled process from the operation device via an output memory.