PURPOSE: To enable the retrieval of data at a high speed.

CONSTITUTION: When retrieving a retrieval character string (ABCA) corresponding to a character string (BABCABB...), which is successively stored in the associated memory cell sequences of an associated memory 26, to be retrieved, the data of the 1st character (A) in the retrieval character string are inputted to a buffer 56 and a comparing operation is performed for all the cell sequences. The operation of comparison with the next character (B) is performed only for the cell sequence of addresses (2) and (5) adjacent with the cell sequence coincident the last time. Similarly, the operation of comparison with the next character (C) is performed only for the cell sequence of addresses (3) and (6). Further, the comparison with the final character (A) is performed only for the cell sequence of an address (4) adjacent to the cell sequence of the address (3) coincident the last time. In this case, even when the length of the retrieval character string is a variable length, only the number of times to repeat the comparing operation is changed and especially when the character string to be retrieved is long, retrieval processing is completed within an extremely short time in comparison with conventional device.