A serial/parallel data conversion apparatus and a method thereof are used to convert serial data into parallel data by a delay pulse and three stage registers, wherein the device includes a first data register, a second data register, a third data register, a frequency divider and a delay controller. Moreover, the first data register converts the serial data into the parallel data according to a first working clock signal. The frequency divider performs a frequency division for the first working clock signal for producing a second working clock signal. The second data register acquires the parallel data from the first register according to the second working clock signal. The delay controller delays the second working clock signal to produce a third working clock signal. Finally, the third data register obtains the parallel data from the second register according to the third working clock signal.