Abstract: A parallel-to-serial converter multiplexes parallel input data into a serial output data. This converter includes a multiplier for multiplying an input clock corresponding to a parallel input data, a divider for dividing the multiplied clock, and a waveform shaping circuit for shaping a serial output data by the multiplied clock. The converter multiplexes parallel data at a center of each phase thereof based on the divided clock by adjusting phases between the input data (or the input clock) and the divided clock to be in a predetermined relationship.