A context-based adaptive binary arithmetic coding (CABAC) decoding device and a coding method thereof are provided. The device comprises: a context memory address calculator, calculating an address identifying a memory location in a context model memory for storage of a context model in next cycle; a mixed context memory, in which the context model of the context memory address calculator is stored and from which the context model is read; a two-bin context adaptive binary arithmetic decoder, outputting several parameters for updating the range and offset of the context model, based on the context model of the mixed context memory and deciding several bins; and a binary syntax element comparator, judging whether a current binary sequence corresponds to the value of syntax elements, based on the bins so as to select a correct memory address.