In an apparatus such as a turbo decoding apparatus in which it is necessary to carry out interleave operation and deinterleave operation, there are provided a memory unit (5) and a memory control unit (12) capable of changing data writing order and data reading order with respect to the memory unit (5) depending on whether data is to be interleaved or deinterleaved. With this arrangement, the single unit of memory (5) can function as an interleaver and a deinterleaver, thereby reducing the size and cost the device.