A data retrieval system includes a retrieval request block for generating a retrieval key including a current state number and a current character string including N characters latched from an input character string, and a state transition memory operating for retrieval based on a state transition table. The state transition table includes a plurality of input entries each including a combination of a current state number and a character pattern string having N characters, and a plurality of output entries each including combination of a next state number and a pattern number of a character pattern retrieved from the input character string. The state transition memory operates for a plurality of retrievals in parallel retrieval processing.