A serial controller is adapted to receive an external clock and an input data, and output an inverted clock and an output data. The serial controller includes an inverter, a serial position detector, a synchronous clock generator, a serial register, and a half-cycle delay unit. Thereby, through the serial controller, the problem that the data signal and the driving clock are not synchronous when the clock series are inverted is avoided. Besides, a bi-directional serial controller further includes an identification unit and a data directing unit, and the serial controller is enabled to return the current status to a central control unit to serve as the reference for error detection.