Abstract: The present invention relates to a data retrieval apparatus for retrieving the data from a number of places of data stored in memories which adopts binary search method and enables high-speed retrieval operation. The apparatus includes three memories and address converting circuits. A logical address space is divided into 2 banks of a bank constituting a set of even number addresses and a bank constituting a set of odd number addresses. Further, in the case where in respect of one bank of the 2 banks and addresses are expressed by binary numbers, the one bank is divided into a bank constituting a set of addresses where an even number of bits of “1” are present and a bank constituting a set of addresses where an odd number of bits of “1” are present. A total of the 3 banks of the logical address space are mapped in a physical address space of 3 memories. A control device carries out retrieval of data stored in the memories by binary search method by using given key data.