An interleaver provision method for providing a continuous length, an interleaving method, and a turbo-encoder thereof are disclosed. The interleaving method selects a basic interleaver having a proper length from among the basic interleaver set, which is predetermined to have the length represented by a multiple of the ARP fluctuation vector period. The interleaving method performs the dummy insertion and the pruning process to have the length acting as the basic-interleaver length, so that it can provide the ARP interleaver having a continuous length.