An grouping bits interleaver includes a grouping bits unit and a data storage unit. The grouping bits unit is used for storing N data bits of an input data and outputting an address signal. Wherein each data bit is stored according to a bit position. The data storage unit coupled to the grouping bits unit is used for saving the content of the grouping bits according to the address signal. Compared to the conventional interleaver, the grouping bits interleaver has better memory usage, less access time, and smaller memory size.